BACKGROUND: The number of reported pertussis has increased in the last two decades. However, many cases of pertussis may be underreported or not diagnosed. The World Health Organization estimates that pertussis causes 200,000-400,000 deaths each year, most deaths are in infants and in developing countries. Infants with pertussis can indicate an undetected source cases in the community. METHODS: At a University Hospital in Brazil individuals that had frequent contacts with a child with confirmed pertussis (the index case) and had recent history of cough were enrolled into the study. Nasopharyngeal swabs were collected from every contact that had cough within the last 21 days. Cases confirmation followed the guidelines of the Center for Disease Control and Prevention-Atlanta, USA. RESULTS: Pertussis diagnosis was confirmed in 51 children, (considered the index cases). Among the index cases, 72.5% (37/51) were under 6 months of age; culture for Bordetella pertussis was positive in 78.4% (40/51). Pertussis was confirmed in 39% (107/276) of the contacts of 51 index cases. Among these contacts identified as a pertussis case, 40.2% (43/107) were between 6 months and 111/2 years of age and 59.8% (64/107) were older than 111/2 years of age. Pertussis was confirmed by culture in 11.2% (12/107) of them and by epidemiologic linkage in 88.8% (95/107). Each index case allowed identifying two new cases of pertussis. CONCLUSION: Public health authorities should consider implementing early recognition of pertussis index cases and searching for pertussis cases among the contacts. Treatment of the cases and prophylaxis of the contacts is fundamental to control outbreaks in the community

American Academy of Pediatrics

D Guris

G De Serres

JM Tuyen

K Bisgard

KM Bisgard

KM Edwards

Laura C Rodrigues

M Tanaka

Pan American Health Organization

Paulo N Baptista

PN Baptista

T Murphy

Vera S Magalhães

English

PubMed

Springer - Publisher Connector

BioMed CentralBMC Pediatrics
ssOpen AcceResearch article
Children with pertussis inform the investigation of other pertussis 
cases among contacts
Paulo N Baptista*†1, Vera S Magalhães†2 and Laura C Rodrigues†3
Address: 1Pediatric Infectious Diseases Service, School Hospital, University of Pernambuco, Recife, Brazil, 2Tropical Medicine Department, Federal 
University of Pernambuco, Recife, Brazil and 3Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, 
University of London, London, UK
Email: Paulo N Baptista* - paulonbaptista@fcm.upe.br; Vera S Magalhães - vemagalhaes@uol.com.br; 
Laura C Rodrigues - Laura.Rodrigues@lshtm.ac.uk
* Corresponding author    †Equal contributors
Abstract
Background: The number of reported pertussis has increased in the last two decades. However,
many cases of pertussis may be underreported or not diagnosed. The World Health Organization
estimates that pertussis causes 200.000 – 400.000 deaths each year, most deaths are in infants and
in developing countries. Infants with pertussis can indicate an undetected source cases in the
community.
Methods: At a University Hospital in Brazil individuals that had frequent contacts with a child with
confirmed pertussis (the index case) and had recent history of cough were enrolled into the study.
Nasopharyngeal swabs were collected from every contact that had cough within the last 21 days.
Cases confirmation followed the guidelines of the Center for Disease Control and Prevention –
Atlanta, U.S.A.
Results: Pertussis diagnosis was confirmed in 51 children, (considered the index cases). Among
the index cases, 72.5% (37/51) were under 6 months of age; culture for Bordetella pertussis was
positive in 78.4% (40/51). Pertussis was confirmed in 39% (107/276) of the contacts of 51 index
cases. Among these contacts identified as a pertussis case, 40.2% (43/107) were between 6 months
and 111/2 years of age and 59.8% (64/107) were older than 111/2 years of age. Pertussis was
confirmed by culture in 11.2% (12/107) of them and by epidemiologic linkage in 88.8% (95/107).
Each index case allowed identifying two new cases of pertussis.
Conclusion: Public health authorities should consider implementing early recognition of pertussis
index cases and searching for pertussis cases among the contacts. Treatment of the cases and
prophylaxis of the contacts is fundamental to control outbreaks in the community.
Background
Pertussis is an endemic disease, with peaks every three to
four years worldwide. Incidence of pertussis has declined,
however many cases of pertussis may be underreported or
not diagnosed. The World Health Organization estimates
that 200.000 – 400.000 deaths occur each year, most
deaths occur in infants and in developing countries [1].
Pertussis in infants younger one year of age should be con-
siders an indicator of undetected disease in the commu-
nity [2].
Published: 22 May 2007
BMC Pediatrics 2007, 7:21 doi:10.1186/1471-2431-7-21
Received: 3 October 2006
Accepted: 22 May 2007
This article is available from: http://www.biomedcentral.com/1471-2431/7/21
© 2007 Baptista et al; licensee BioMed Central Ltd. 
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), 
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Page 1 of 4
(page number not for citation purposes)
BMC Pediatrics 2007, 7:21 http://www.biomedcentral.com/1471-2431/7/21The transmissibility period of an individual with pertussis
is around 21 days, but some can transmit for a longer
period. Suspect cases and cases of pertussis should be iso-
lated from young children, infants, child care centers,
schools and public gatherings. The transmissibility period
can be decreased and isolation ended after the fifth day of
anti-pertussis antibiotic therapy [1]. Adolescents and
adults have an important role as source of pertussis infec-
tion, particularly for these younger than one year of age
[3,4]. In this age group, pertussis is frequently severe and
hospitalization is often required [5]. Pertussis diagnosis
among adolescents and adults is often missed or mistaken
as another respiratory disease. In the last years, increased
awareness of pertussis among adolescents and adults and
more sensitive diagnostic tests (like serology and
polymerase chain reaction assays) have contributed to
increase the number of confirmed pertussis in this age
group [6,7].
In Brazil until 2004, pertussis whole cell vaccine was given
at 2, 4 and 6 months of age and a booster dose was given
between 15 and 18 months of age. In the study area, per-
tussis vaccine coverage for 3 doses among children
younger than one year of age was higher than 96%. The
study of vaccine effectiveness in contacts revealed a low
vaccine effectiveness against clinical disease, 12.5% (com-
pared to children who received one dose only). On the
other hand, vaccine effectiveness in reducing the transmis-
sibility of a vaccinated primary case aged 7 months to 5
years old was 61.6%. This may have a significant effect in
reducing circulation of B. pertussis in the studied popula-
tion [8].
In 2003, in the Oswaldo Cruz School Hospital – Brazil, we
followed the guidelines of the Center for Disease Control
and Prevention – Atlanta, U.S.A. for pertussis diagnosis.
[9]. Pertussis was confirmed in 158 individuals. In this
year, most of children with pertussis were infants younger
one year of age. Pertussis in infants younger one year of
age should be considers an indicator of undetected dis-
ease in the community [2]. The objective of this study was
to identify individuals with pertussis among the contacts
of children with confirmed pertussis.
Methods
In 2003, in the Oswaldo Cruz School Hospital (a metro-
politan sentinel surveillance hospital for infectious dis-
eases), children referred to the hospital with suspected
pertussis and that had this diagnosis confirmed were iden-
tified as index cases. Children were considered a suspected
case of pertussis if they had a cough illness lasting at least
7 days, with either paroxysms of coughing, inspiratory
"whoop", post-tussive vomiting or cyanosis during the
paroxysms of coughing without other apparent cause.
Household members, neighbors and relatives that had
frequent contacts with the index cases were enrolled into
the study. Parents/guardians were interviewed, and infor-
mation collected for the contacts of the index cases on
recent history of cough. Every contacts of a confirmed case
of pertussis with recent history of cough were requested to
attend to the hospital.
Nasopharyngeal swabs were collected from every index
cases and every contacts of the index cases that had cough
within the last 21 days and had attended to the Hospital.
Culture procedure followed the guidelines of the Centre
for Disease Control and Prevention – Atlanta, U.S.A [10].
Clinical specimens were placed in Regan Lowe medium
and incubated at 35°C to 37°C. Cultures were checked to
up 12 days. Bordetella pertussis culture was confirmed by
biochemistry test. Cultures were not collected from sub-
jects with no reported symptoms. Although asymptomatic
carriers exist, they are not relevant for transmission [11].
The household members, including the case attending the
Oswaldo Cruz School Hospital, were classified: index case
– the case that was first reported to the hospital; primary
case – first individual in the household that presented
cough and had pertussis diagnosis confirmed; co-primary
case – had symptoms onset within 6 days after the onset
in the primary case; secondary case – had symptoms onset
7 or more days after onset in the primary case; Not a case
of pertussis – contacts without pertussis symptoms [9].
The index cases and their contacts were considered con-
firmed cases of pertussis if they had one of: 1. an illness
with cough of any duration and positive culture for B. per-
tussis; 2. an illness with cough lasting at least two weeks
and at least one of the following symptoms: paroxysm of
coughing, inspiratory whooping, pos-tussive vomiting, a
negative culture but a epidemiologic link to a culture con-
firmed case; 3. an illness with cough lasting at least 14
days, in a household with two or more pertussis cases,
where there were one culture confirmed case (a house-
hold outbreak).
Statistical analysis: Statistical significance was assessed
using chi square (Fisher exact test when the value of one
of the cells in a table was <5). A confidence interval of
95% was calculated and "p" was considered significant
when ≤0.05. The study was approved by the Ethics Com-
mittee of HUOC. Parents/guardians signed a written con-
sent form to participate.
Results
Among 287 children assisted for suspect pertussis in the
Pediatric Infectious Disease Service in the HUOC, pertus-
sis diagnosis was confirmed in 51 (the index cases).Page 2 of 4
(page number not for citation purposes)
BMC Pediatrics 2007, 7:21 http://www.biomedcentral.com/1471-2431/7/21All index cases were under 111/2 years of age, 92.2%(10/
51) were under 5 years and 72.5% (37/51) were under 6
months of age. Among the contacts of the index cases that
were identified as a pertussis case, 40.2% (43/107) were
between 6 months and 111/2 years of age and 59.8% (64/
107) were older than 111/2 years of age.
Pertussis vaccine report was obtained from the index
cases: 72.5%(37/51) were not vaccinated or had received
<3 doses and 25.5%(13/51) had received 3 or 4 doses of
the vaccine. One patient didn't have information on his
vaccine schedule. The difference between the group that
was unvaccinated or received < 3 doses and these that
received 3 or 4 doses was statistically significant. P < 0.01
Culture of nasopharyngeal swab was positive for Borde-
tella pertussis in 78.4% (40/51) of the index cases and neg-
ative in 19.6% (10/51) of them. One index case was in use
of erythromycin for more than 5 days and swab for culture
was not collected. All index cases met the clinical case def-
inition for pertussis. Pertussis was confirmed by culture in
78.4%(40/51) of index cases and by epidemiologic link-
age in 21.6% (11/51). Among the contacts of the index
cases that were identified as a pertussis case, pertussis was
confirmed by culture in 11.2%(12/107) and by epidemi-
ologic linkage in 88.8%(95/107). A quarter of pertussis
cases identified by the index cases were confirmed by out-
break case definition in household settings.
Twenty-two contacts were excluded because information
about them was insufficient to classify them into cases or
not cases. Two parents report relatives with cough who
did not attend to the hospital. Some parents reported
neighbors with history of cough, but they did not attend
to the hospital as they were not household contacts.
All the contact cases identified by the index cases were rel-
atives (figure 1). Among the contacts, 56%(60/107) of the
pertussis cases were women and 44%(47/107) were man
chi2 3,68 P = 0,05. Many relative were living in the same
household, the same street or the same neighborhood.
The ones that were living in different neighborhoods used
to spend the week-end together in the same household.
Everyone who have had contact with the index case and
did not have cough when examined received chemo-
prophylaxis. The index cases and secondary cases received
treatment to pertussis as indicated by the Brazilian Health
Ministry. Among 298 household contacts, pertussis was
confirmed in 107 subjects. Each index case allowed iden-
tifying 2 new cases of pertussis. (Table 1)
Discussion
In this study, nasopharyngeal culture was the only labora-
tory test used to confirm the diagnosis. It is likely that
more cases would have been confirmed if serology and
polimerase chain reaction assays were available. Finally, it
is possible that some individuals in which the pertussis
was confirmed using the "household outbreak criteria"
(cough lasting at least 14 days, in a household with two or
more pertussis cases, where there was one culture con-
firmed case) may have had another respiratory disease
and have been misclassified.
This study was achieved in a service of pediatric infectious
disease. This is likely to have contributed to the fact that
all index cases were under 111/2 years of age. However,
children, particularly infants under one year of age fre-
quently have severe pertussis and often require medical
assistance [5]. This may in part explain the observation
that three quarters of the index cases were under six
months of age. This may also have contributed to the
extremely high compliance resulting in almost all relatives
of the index cases attending the hospital.
In the study, all adults with confirmed pertussis have pre-
sented symptoms that suggested the diagnosis of pertus-
sis. Adolescents and adults are important source of
pertussis infection for infant and even for others adults
[3,4,12]. In the study, the primary case – the source of
infection to the household – was older than 11 and a half
years for 79% (66/84) of all secondary cases and for
Table 1: Classification of the index cases and of cases identified 
by index case in Oswaldo Cruz School Hospital in Brazil.
Classification
Primary Co-primary Secondary Total
Index cases 18 (35.2%) 2(4%) 31(60.8%) 51
Cases identified by 
index case
39(36.4%) 6(5.6%) 62(58%) 107
Total 57 8 93 158
Pertussis cases among relatives of the index casesFigure 1
Pertussis cases among relatives of the index cases.
Index Cases 
51
Mothers
13
Fathers 
7
Brothers 
18
Sisters
10
Grand-Fathers 
2
Aunts
15
Grand-Mothers
6
Uncles 
9
Male Cousins 
11
Female Cousins
16Page 3 of 4
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76%(19/25) of the secondary case under 6 months of age
[3]. Pertussis in a child under one year of age informs to
investigate other pertussis cases among contacts [2].
Culture for B. pertussis has a low specificity for pertussis
diagnosis and is often negative among vaccinated individ-
uals and adults with Pertussis [10]. The fact that three
forth of the index cases were unvaccinated or incom-
pletely vaccinated may have contributed to the observa-
tion of positive culture in 78% of them.
Each index case in this research allowed the diagnosis of
two other pertussis cases among the close contacts. The
fact that the index cases and secondary cases were treated
with antibiotics and the contacts without cough received
chemoprophylaxis may have reduced the spread of pertus-
sis among the contacts.
Public health authorities should consider implementing
case finding in the community, particularly among infants
younger one year of age, an important indicator of unde-
tected cases in the community. Ideally, in addition to
nasopharyngeal culture for B. pertussis, a more sensitive
diagnosis test like PCR should be introduced to optimize
the identification of new cases.
Conclusion
Health care professional should be in alert to identify new
cases of pertussis. The early recognition of pertussis index
cases by health care professionals, the treatment of the
cases and prophylaxis of the contacts is fundamental to
control an outbreak in the community.
Competing interests
This research received grants from the Pan-American
Health Organization/World Health Organization
Authors' contributions
P.N. Baptista and V. Magalhães conceived the study and
supervised all aspects of its implementation. L. C. Rod-
rigues synthesized analyses and led the writing.
Acknowledgements
The authors are grateful to the Pertussis Laboratory Program – Center for 
Disease Control and Prevention, Atlanta – USA that have contributed 
materials for the isolation of the Bordetella pertussis. The authors are also 
grateful to Professor Marcelo Magalhães and Nadjla Ferreira who have 
done the culture to isolate the Bordetella pertussis.
References
1. Pan American Health Organization: Control of diphtheria, per-
tussis, Haemophilus influenzae type b, and hepatitis B: field
guide.  2005 [http://www.paho.org/english/ad/fch/im/
fieldguide_pentavalent.pdf]. Washington, DC: PAHO
2. Tuyen JM, Bisgard K: Community Settings.  Pertussis Guide 2000,
Cap 11: [http://www.cdc.gov/vaccines/pubs/pertussis-guide/down
loads/chapter10.pdf]. Center for Disease Control and Prevention:
USA Accessed: September 18, 2002
3. Baptista PN, Magalhães V, Rodrigues LC, Rocha MAW, Pimentel AM:
Source of infection in household transmission of culture-con-
firmed pertussis in Brazil.  Pediatr Infect Dis J 2005,
24(11):1027-28.
4. Bisgard KM, Pascual B, Ehresmann KR, et al.: Infant Pertussis, who
is the source?  Pediatr Infect Dis J 2004, 23:985-989.
5. Tanaka M, Vitek CR, Pascual FB, et al.: Trends in pertussis among
infants in the United States, 1980–1999.  JAMA 2003,
2309:2968-2975.
6. De Serres G, Shadmani R, Duval B, et al.: Morbidity of pertussis in
adolescents and adults.  J Infect Dis 2000, 182:174-179.
7. Guris D, Strebel PM, Bardenheier B, et al.: Changing epidemiology
of pertussis in the United States: increasing reported inci-
dence among adolescents and adults, 1990–1996.  Clin Infect
Dis 1999, 28:1230-1237.
8. Baptista PN, Magalhães V, Rodrigues LC, et al.: Pertussis vaccine
effectiveness in reducing clinical disease, transmissibility and
bacteriologically positive cases after household exposure in
Brazil.  Pediatr Infect Dis J 2005, 25(09):844-846.
9. Bisgard K: Definitions.  Pertussis Guide 2000, Cap 11: [http://
www.cdc.gov/nip/publications/pertussis/guide.htm]. Center for Dis-
ease Control and Prevention: USA Accessed: September 18, 2002
10. Murphy T, Bisgard K, Sanden G: Diagnosis and Laboratory Meth-
ods.  Pertussis Guide 2000 [http://www.cdc.gov/nip/publications/per
tussis/guide.htm]. Center for Disease Control and Prevention:
Atlanta, GA Accessed: September 18, 2002
11. American Academy of Pediatrics: Pertussis.  In 2000 Red Book:
Report of the Committee on Infectious Diseases 25th edition. Edited by:
Pickering LK. Elk Grove Village, IL: American Academy of pediatrics;
2000:435-448. 
12. Edwards KM: Overview of pertussis: focus on epidemiology,
source of infection and long term protection after infant vac-
cination.  Pediatr Infect Dis J 2005, 24(suppl):S109-S116.
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Children with pertussis inform the investigation of other pertussis cases among contacts

Abstract Background The number of reported pertussis has increased in the last two decades. However, many cases of pertussis may be underreported or not diagnosed. The World Health Organization estimates that pertussis causes 200.000 – 400.000 deaths each year, most deaths are in infants and in developing countries. Infants with pertussis can indicate an undetected source cases in the community. Methods At a University Hospital in Brazil individuals that had frequent contacts with a child with confirmed pertussis (the index case) and had recent history of cough were enrolled into the study. Nasopharyngeal swabs were collected from every contact that had cough within the last 21 days. Cases confirmation followed the guidelines of the Center for Disease Control and Prevention – Atlanta, U.S.A. Results Pertussis diagnosis was confirmed in 51 children, (considered the index cases). Among the index cases, 72.5% (37/51) were under 6 months of age; culture for Bordetella pertussis was positive in 78.4% (40/51). Pertussis was confirmed in 39% (107/276) of the contacts of 51 index cases. Among these contacts identified as a pertussis case, 40.2% (43/107) were between 6 months and 111/2 years of age and 59.8% (64/107) were older than 111/2 years of age. Pertussis was confirmed by culture in 11.2% (12/107) of them and by epidemiologic linkage in 88.8% (95/107). Each index case allowed identifying two new cases of pertussis. Conclusion Public health authorities should consider implementing early recognition of pertussis index cases and searching for pertussis cases among the contacts. Treatment of the cases and prophylaxis of the contacts is fundamental to control outbreaks in the community.</p

Rodrigues Laura C

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Baptista, PN; Magalhaes, VS; Rodrigues, LC (2007) Children withpertussis inform the investigation of other pertussis cases among con-tacts. BMC Pediatr, 7. p. 21. ISSN 1471-2431Downloaded from: http://researchonline.lshtm.ac.uk/9190/Usage GuidelinesPlease refer to usage guidelines at http://researchonline.lshtm.ac.uk/policies.html or alterna-tively contact researchonline@lshtm.ac.uk.Available under license: Creative Commons Attribution http://creativecommons.org/licenses/by/2.5/BioMed CentralPage 1 of 4(page number not for citation purposes)BMC PediatricsOpen AccessResearch articleChildren with pertussis inform the investigation of other pertussis cases among contactsPaulo N Baptista*†1, Vera S Magalhães†2 and Laura C Rodrigues†3Address: 1Pediatric Infectious Diseases Service, School Hospital, University of Pernambuco, Recife, Brazil, 2Tropical Medicine Department, Federal University of Pernambuco, Recife, Brazil and 3Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, University of London, London, UKEmail: Paulo N Baptista* - paulonbaptista@fcm.upe.br; Vera S Magalhães - vemagalhaes@uol.com.br; Laura C Rodrigues - Laura.Rodrigues@lshtm.ac.uk* Corresponding author    †Equal contributorsAbstractBackground: The number of reported pertussis has increased in the last two decades. However,many cases of pertussis may be underreported or not diagnosed. The World Health Organizationestimates that pertussis causes 200.000 – 400.000 deaths each year, most deaths are in infants andin developing countries. Infants with pertussis can indicate an undetected source cases in thecommunity.Methods: At a University Hospital in Brazil individuals that had frequent contacts with a child withconfirmed pertussis (the index case) and had recent history of cough were enrolled into the study.Nasopharyngeal swabs were collected from every contact that had cough within the last 21 days.Cases confirmation followed the guidelines of the Center for Disease Control and Prevention –Atlanta, U.S.A.Results: Pertussis diagnosis was confirmed in 51 children, (considered the index cases). Amongthe index cases, 72.5% (37/51) were under 6 months of age; culture for Bordetella pertussis waspositive in 78.4% (40/51). Pertussis was confirmed in 39% (107/276) of the contacts of 51 indexcases. Among these contacts identified as a pertussis case, 40.2% (43/107) were between 6 monthsand 111/2 years of age and 59.8% (64/107) were older than 111/2 years of age. Pertussis wasconfirmed by culture in 11.2% (12/107) of them and by epidemiologic linkage in 88.8% (95/107).Each index case allowed identifying two new cases of pertussis.Conclusion: Public health authorities should consider implementing early recognition of pertussisindex cases and searching for pertussis cases among the contacts. Treatment of the cases andprophylaxis of the contacts is fundamental to control outbreaks in the community.BackgroundPertussis is an endemic disease, with peaks every three tofour years worldwide. Incidence of pertussis has declined,however many cases of pertussis may be underreported ornot diagnosed. The World Health Organization estimatesthat 200.000 – 400.000 deaths occur each year, mostdeaths occur in infants and in developing countries [1].Pertussis in infants younger one year of age should be con-siders an indicator of undetected disease in the commu-nity [2].Published: 22 May 2007BMC Pediatrics 2007, 7:21 doi:10.1186/1471-2431-7-21Received: 3 October 2006Accepted: 22 May 2007This article is available from: http://www.biomedcentral.com/1471-2431/7/21© 2007 Baptista et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.BMC Pediatrics 2007, 7:21 http://www.biomedcentral.com/1471-2431/7/21Page 2 of 4(page number not for citation purposes)The transmissibility period of an individual with pertussisis around 21 days, but some can transmit for a longerperiod. Suspect cases and cases of pertussis should be iso-lated from young children, infants, child care centers,schools and public gatherings. The transmissibility periodcan be decreased and isolation ended after the fifth day ofanti-pertussis antibiotic therapy [1]. Adolescents andadults have an important role as source of pertussis infec-tion, particularly for these younger than one year of age[3,4]. In this age group, pertussis is frequently severe andhospitalization is often required [5]. Pertussis diagnosisamong adolescents and adults is often missed or mistakenas another respiratory disease. In the last years, increasedawareness of pertussis among adolescents and adults andmore sensitive diagnostic tests (like serology andpolymerase chain reaction assays) have contributed toincrease the number of confirmed pertussis in this agegroup [6,7].In Brazil until 2004, pertussis whole cell vaccine was givenat 2, 4 and 6 months of age and a booster dose was givenbetween 15 and 18 months of age. In the study area, per-tussis vaccine coverage for 3 doses among childrenyounger than one year of age was higher than 96%. Thestudy of vaccine effectiveness in contacts revealed a lowvaccine effectiveness against clinical disease, 12.5% (com-pared to children who received one dose only). On theother hand, vaccine effectiveness in reducing the transmis-sibility of a vaccinated primary case aged 7 months to 5years old was 61.6%. This may have a significant effect inreducing circulation of B. pertussis in the studied popula-tion [8].In 2003, in the Oswaldo Cruz School Hospital – Brazil, wefollowed the guidelines of the Center for Disease Controland Prevention – Atlanta, U.S.A. for pertussis diagnosis.[9]. Pertussis was confirmed in 158 individuals. In thisyear, most of children with pertussis were infants youngerone year of age. Pertussis in infants younger one year ofage should be considers an indicator of undetected dis-ease in the community [2]. The objective of this study wasto identify individuals with pertussis among the contactsof children with confirmed pertussis.MethodsIn 2003, in the Oswaldo Cruz School Hospital (a metro-politan sentinel surveillance hospital for infectious dis-eases), children referred to the hospital with suspectedpertussis and that had this diagnosis confirmed were iden-tified as index cases. Children were considered a suspectedcase of pertussis if they had a cough illness lasting at least7 days, with either paroxysms of coughing, inspiratory"whoop", post-tussive vomiting or cyanosis during theparoxysms of coughing without other apparent cause.Household members, neighbors and relatives that hadfrequent contacts with the index cases were enrolled intothe study. Parents/guardians were interviewed, and infor-mation collected for the contacts of the index cases onrecent history of cough. Every contacts of a confirmed caseof pertussis with recent history of cough were requested toattend to the hospital.Nasopharyngeal swabs were collected from every indexcases and every contacts of the index cases that had coughwithin the last 21 days and had attended to the Hospital.Culture procedure followed the guidelines of the Centrefor Disease Control and Prevention – Atlanta, U.S.A [10].Clinical specimens were placed in Regan Lowe mediumand incubated at 35°C to 37°C. Cultures were checked toup 12 days. Bordetella pertussis culture was confirmed bybiochemistry test. Cultures were not collected from sub-jects with no reported symptoms. Although asymptomaticcarriers exist, they are not relevant for transmission [11].The household members, including the case attending theOswaldo Cruz School Hospital, were classified: index case– the case that was first reported to the hospital; primarycase – first individual in the household that presentedcough and had pertussis diagnosis confirmed; co-primarycase – had symptoms onset within 6 days after the onsetin the primary case; secondary case – had symptoms onset7 or more days after onset in the primary case; Not a caseof pertussis – contacts without pertussis symptoms [9].The index cases and their contacts were considered con-firmed cases of pertussis if they had one of: 1. an illnesswith cough of any duration and positive culture for B. per-tussis; 2. an illness with cough lasting at least two weeksand at least one of the following symptoms: paroxysm ofcoughing, inspiratory whooping, pos-tussive vomiting, anegative culture but a epidemiologic link to a culture con-firmed case; 3. an illness with cough lasting at least 14days, in a household with two or more pertussis cases,where there were one culture confirmed case (a house-hold outbreak).Statistical analysis: Statistical significance was assessedusing chi square (Fisher exact test when the value of oneof the cells in a table was <5). A confidence interval of95% was calculated and "p" was considered significantwhen ≤0.05. The study was approved by the Ethics Com-mittee of HUOC. Parents/guardians signed a written con-sent form to participate.ResultsAmong 287 children assisted for suspect pertussis in thePediatric Infectious Disease Service in the HUOC, pertus-sis diagnosis was confirmed in 51 (the index cases).BMC Pediatrics 2007, 7:21 http://www.biomedcentral.com/1471-2431/7/21Page 3 of 4(page number not for citation purposes)All index cases were under 111/2 years of age, 92.2%(10/51) were under 5 years and 72.5% (37/51) were under 6months of age. Among the contacts of the index cases thatwere identified as a pertussis case, 40.2% (43/107) werebetween 6 months and 111/2 years of age and 59.8% (64/107) were older than 111/2 years of age.Pertussis vaccine report was obtained from the indexcases: 72.5%(37/51) were not vaccinated or had received<3 doses and 25.5%(13/51) had received 3 or 4 doses ofthe vaccine. One patient didn't have information on hisvaccine schedule. The difference between the group thatwas unvaccinated or received < 3 doses and these thatreceived 3 or 4 doses was statistically significant. P < 0.01Culture of nasopharyngeal swab was positive for Borde-tella pertussis in 78.4% (40/51) of the index cases and neg-ative in 19.6% (10/51) of them. One index case was in useof erythromycin for more than 5 days and swab for culturewas not collected. All index cases met the clinical case def-inition for pertussis. Pertussis was confirmed by culture in78.4%(40/51) of index cases and by epidemiologic link-age in 21.6% (11/51). Among the contacts of the indexcases that were identified as a pertussis case, pertussis wasconfirmed by culture in 11.2%(12/107) and by epidemi-ologic linkage in 88.8%(95/107). A quarter of pertussiscases identified by the index cases were confirmed by out-break case definition in household settings.Twenty-two contacts were excluded because informationabout them was insufficient to classify them into cases ornot cases. Two parents report relatives with cough whodid not attend to the hospital. Some parents reportedneighbors with history of cough, but they did not attendto the hospital as they were not household contacts.All the contact cases identified by the index cases were rel-atives (figure 1). Among the contacts, 56%(60/107) of thepertussis cases were women and 44%(47/107) were manchi2 3,68 P = 0,05. Many relative were living in the samehousehold, the same street or the same neighborhood.The ones that were living in different neighborhoods usedto spend the week-end together in the same household.Everyone who have had contact with the index case anddid not have cough when examined received chemo-prophylaxis. The index cases and secondary cases receivedtreatment to pertussis as indicated by the Brazilian HealthMinistry. Among 298 household contacts, pertussis wasconfirmed in 107 subjects. Each index case allowed iden-tifying 2 new cases of pertussis. (Table 1)DiscussionIn this study, nasopharyngeal culture was the only labora-tory test used to confirm the diagnosis. It is likely thatmore cases would have been confirmed if serology andpolimerase chain reaction assays were available. Finally, itis possible that some individuals in which the pertussiswas confirmed using the "household outbreak criteria"(cough lasting at least 14 days, in a household with two ormore pertussis cases, where there was one culture con-firmed case) may have had another respiratory diseaseand have been misclassified.This study was achieved in a service of pediatric infectiousdisease. This is likely to have contributed to the fact thatall index cases were under 111/2 years of age. However,children, particularly infants under one year of age fre-quently have severe pertussis and often require medicalassistance [5]. This may in part explain the observationthat three quarters of the index cases were under sixmonths of age. This may also have contributed to theextremely high compliance resulting in almost all relativesof the index cases attending the hospital.In the study, all adults with confirmed pertussis have pre-sented symptoms that suggested the diagnosis of pertus-sis. Adolescents and adults are important source ofpertussis infection for infant and even for others adults[3,4,12]. In the study, the primary case – the source ofinfection to the household – was older than 11 and a halfyears for 79% (66/84) of all secondary cases and forTable 1: Classification of the index cases and of cases identified by index case in Oswaldo Cruz School Hospital in Brazil.ClassificationPrimary Co-primary Secondary TotalIndex cases 18 (35.2%) 2(4%) 31(60.8%) 51Cases identified by index case39(36.4%) 6(5.6%) 62(58%) 107Total 57 8 93 158Pertussis cases among relatives of the index casesFigure 1Pertussis cases among relatives of the index cases.Index Cases 51Mothers13Fathers 7Brothers 18Sisters10Grand-Fathers 2Aunts15Grand-Mothers6Uncles 9Male Cousins 11Female Cousins16Publish with BioMed Central   and  every scientist can read your work free of charge"BioMed Central will be the most significant development for disseminating the results of biomedical research in our lifetime."Sir Paul Nurse, Cancer Research UKYour research papers will be:available free of charge to the entire biomedical communitypeer reviewed and published immediately upon acceptancecited in PubMed and archived on PubMed Central yours — you keep the copyrightSubmit your manuscript here:http://www.biomedcentral.com/info/publishing_adv.aspBioMedcentralBMC Pediatrics 2007, 7:21 http://www.biomedcentral.com/1471-2431/7/21Page 4 of 4(page number not for citation purposes)76%(19/25) of the secondary case under 6 months of age[3]. Pertussis in a child under one year of age informs toinvestigate other pertussis cases among contacts [2].Culture for B. pertussis has a low specificity for pertussisdiagnosis and is often negative among vaccinated individ-uals and adults with Pertussis [10]. The fact that threeforth of the index cases were unvaccinated or incom-pletely vaccinated may have contributed to the observa-tion of positive culture in 78% of them.Each index case in this research allowed the diagnosis oftwo other pertussis cases among the close contacts. Thefact that the index cases and secondary cases were treatedwith antibiotics and the contacts without cough receivedchemoprophylaxis may have reduced the spread of pertus-sis among the contacts.Public health authorities should consider implementingcase finding in the community, particularly among infantsyounger one year of age, an important indicator of unde-tected cases in the community. Ideally, in addition tonasopharyngeal culture for B. pertussis, a more sensitivediagnosis test like PCR should be introduced to optimizethe identification of new cases.ConclusionHealth care professional should be in alert to identify newcases of pertussis. The early recognition of pertussis indexcases by health care professionals, the treatment of thecases and prophylaxis of the contacts is fundamental tocontrol an outbreak in the community.Competing interestsThis research received grants from the Pan-AmericanHealth Organization/World Health OrganizationAuthors' contributionsP.N. Baptista and V. Magalhães conceived the study andsupervised all aspects of its implementation. L. C. Rod-rigues synthesized analyses and led the writing.AcknowledgementsThe authors are grateful to the Pertussis Laboratory Program – Center for Disease Control and Prevention, Atlanta – USA that have contributed materials for the isolation of the Bordetella pertussis. The authors are also grateful to Professor Marcelo Magalhães and Nadjla Ferreira who have done the culture to isolate the Bordetella pertussis.References1. Pan American Health Organization: Control of diphtheria, per-tussis, Haemophilus influenzae type b, and hepatitis B: fieldguide.  2005 [http://www.paho.org/english/ad/fch/im/fieldguide_pentavalent.pdf]. Washington, DC: PAHO2. Tuyen JM, Bisgard K: Community Settings.  Pertussis Guide 2000,Cap 11: [http://www.cdc.gov/vaccines/pubs/pertussis-guide/downloads/chapter10.pdf]. Center for Disease Control and Prevention:USA Accessed: September 18, 20023. Baptista PN, Magalhães V, Rodrigues LC, Rocha MAW, Pimentel AM:Source of infection in household transmission of culture-con-firmed pertussis in Brazil.  Pediatr Infect Dis J 2005,24(11):1027-28.4. Bisgard KM, Pascual B, Ehresmann KR, et al.: Infant Pertussis, whois the source?  Pediatr Infect Dis J 2004, 23:985-989.5. Tanaka M, Vitek CR, Pascual FB, et al.: Trends in pertussis amonginfants in the United States, 1980–1999.  JAMA 2003,2309:2968-2975.6. De Serres G, Shadmani R, Duval B, et al.: Morbidity of pertussis inadolescents and adults.  J Infect Dis 2000, 182:174-179.7. Guris D, Strebel PM, Bardenheier B, et al.: Changing epidemiologyof pertussis in the United States: increasing reported inci-dence among adolescents and adults, 1990–1996.  Clin InfectDis 1999, 28:1230-1237.8. Baptista PN, Magalhães V, Rodrigues LC, et al.: Pertussis vaccineeffectiveness in reducing clinical disease, transmissibility andbacteriologically positive cases after household exposure inBrazil.  Pediatr Infect Dis J 2005, 25(09):844-846.9. Bisgard K: Definitions.  Pertussis Guide 2000, Cap 11: [http://www.cdc.gov/nip/publications/pertussis/guide.htm]. Center for Dis-ease Control and Prevention: USA Accessed: September 18, 200210. Murphy T, Bisgard K, Sanden G: Diagnosis and Laboratory Meth-ods.  Pertussis Guide 2000 [http://www.cdc.gov/nip/publications/pertussis/guide.htm]. Center for Disease Control and Prevention:Atlanta, GA Accessed: September 18, 200211. American Academy of Pediatrics: Pertussis.  In 2000 Red Book:Report of the Committee on Infectious Diseases 25th edition. Edited by:Pickering LK. Elk Grove Village, IL: American Academy of pediatrics;2000:435-448. 12. Edwards KM: Overview of pertussis: focus on epidemiology,source of infection and long term protection after infant vac-cination.  Pediatr Infect Dis J 2005, 24(suppl):S109-S116.Pre-publication historyThe pre-publication history for this paper can be accessedhere:http://www.biomedcentral.com/1471-2431/7/21/prepub

AM: Source of infection in household transmission of culture-confirmed pertussis in Brazil. Pediatr Infect Dis J

American Academy of Pediatrics: Pertussis. I n 2000 Red Book: Report of the Committee on Infectious Diseases 25th edition. Edited by: Pickering LK. Elk Grove Village, IL: American Academy of pediatrics;

Changing epidemiology of pertussis in the United States: increasing reported incidence among adolescents and adults, 1990–1996. Clin Infect Dis

Community Settings. Pertussis Guide 2000, Cap 11: [http://www.cdc.gov/vaccines/pubs/pertussis-guide/down loads/chapter10.pdf]. Center for Disease Control and Prevention:

Health Organization: Control of diphtheria, pertussis, Haemophilus influenzae type b, and hepatitis B: field guide.

Infant Pertussis, who is the source? Pediatr Infect Dis J

Morbidity of pertussis in adolescents and adults.

Overview of pertussis: focus on epidemiology, source of infection and long term protection after infant vaccination. Pediatr Infect Dis J

Pertussis Guide

Pertussis Guide 2000, Cap 11: [http:// www.cdc.gov/nip/publications/pertussis/guide.htm]. Center for Disease Control and Prevention:

Pertussis vaccine effectiveness in reducing clinical disease, transmissibility and bacteriologically positive cases after household exposure in Brazil. Pediatr Infect Dis J

Trends in pertussis among infants in the United States,

Children with pertussis inform the investigation of other pertussis cases among contacts.

http://researchonline.lshtm.ac.uk/9190/1/1471-2431-7-21.pdf

Children with pertussis inform the investigation of other pertussis cases among contacts

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