BACKGROUND: While molluscum contagiosum is considered to be a frequently

          encountered disease, few data on its incidence are known. AIM: The

          objective of this study was to describe the incidence of molluscum

          contagiosum in Dutch general practice and to assess the importance of

          venereal molluscum contagiosum. METHOD: Data were taken from the national

          survey of morbidity and interventions in general practice, drawn from 103

          practices across the Netherlands, with a study population of 332300.

          RESULTS: The infection appeared to be common in childhood (cumulative

          incidence 17% in those aged under 15 years); the adult, sexually

          transmitted, form was rare. Incidence was higher between January and June

          than between July and December. Cases were unequally divided between

          recording practices, which is though to have been caused by the occurrence

          of small epidemics. CONCLUSION: The incidence of molluscum contagiosum in

          Dutch general practice was found to be 2.4 per 1000 person years.

          Molluscum contagiosum should still be considered as a mainly paediatric

          disease

Bruijnzeels, M.A. (Marc)

Koning, S. (Sander)

Suijlekom-Smit, L.W.A. (Lisette) van

Wouden, J.C. (Hans) van der

Erasmus University Digital Repository

Original papersMolluscum contagiosum in Dutch generalpracticeS KONINGM A BRUIJNZEELSL W A VAN SUIJLEKOM-SMITJ C VAN DER WOUDENSUMMARYBackground. While molluscum contagiosum is consideredto be a frequently encountered disease, few data on its incid-ence are known.Aim. The objective of this study was to describe the incid-ence of molluscum contagiosum in Dutch general practiceand to assess the importance of venereal molluscum conta-giosum.Method. Data were taken from the national survey ofmorbidity and interventions in general practice, drawnfrom 103 practices across the Netherlands, with a studypopulation of 332 300.Results. The infection appeared to be common in child-hood (cumulative incidence 17% in those aged under 15years); the adult, sexually transmitted, form was rare.Incidence was higher between January and June thanbetween July and December. Cases were unequally dividedbetween recording practices, which is thought to have beencaused by the occurrence of small epidemics.Conclusion. The incidence of molluscum contagiosum inDutch general practice was found to be 2.4 per 1000 personyears. Molluscum contagiosum should still be consideredas a mainly paediatric disease.Keywords: pox virus infections; skin diseases; morbidity;seasonal morbidity; differential diagnosis.IntroductionM OLLUSCUM contagiosum is a self-limiting, viral cuta-neous infection that has traditionally been regarded as apaediatric disease. Treatment with curettage, cryotherapy orelectrocautery is considered easy. In the last few decades, it hasbecome recognized that there are two different forms: the com-monly known benign skin tumours in children and the sexuallytransmitted disease seen in young adults. Cobbold andMacDonald saw more patients with venereal than paediatric typemolluscum contagiosum in 1970,1 and suggested classification ofmolluscum contagiosum as a sexually transmitted disease. Mostliterature on molluscum contagiosum published since then refersto it as such. The incidence of the venereal form was shown tohave increased dramatically from 1966 to 1983 in the UnitedS Koning, MD, general practitioner trainee; M A Bruijnzeels, MA, dataanalyst; and J C van der Wouden, MA, PhD, research coordinator,Department of General Practice, Erasmus University, Rotterdam,Netherlands. L W A van Suijlekom-Smit, MD, paediatrician, Departmentof Paediatrics, Erasmus University, and University Hospital, SophiaChildren's Hospital, Rotterdam, Netherlands.Submitted: 15 October 1993; accepted: 1 March 1994.C British Journal ofGeneral Practice, 1994, 44, 417-419.States of America,2 as well as in England between 1971 and1982.3 Recently, a third group with molluscum contagiosum hasbeen described: patients with the acquired immune deficiencysyndrome (AIDS) or other immunosuppressive disorders andpatients receiving immunosuppressive therapy.7Even though molluscum contagiosum is commonly consideredto be a frequently encountered disease, 5'6 few reliable data on itsincidence are available.5'68 Studies in a general or paediatricpopulation are scarce and not recent.9-13 They tend to describeepidemics, annual attack rates, or prevalence in a relatively smallor local population. They frequently originate from warm cli-mates, where the infection seems to be more common than inmoderate climates. From general practice, only two brief reportswere found.'4"15The aims of this study were to assess the incidence of mollus-cum contagiosum in Dutch general practice, by age, sex, region,season and degree of urbanization (population size). The hypo-thesis was that molluscum contagiosum in the general populationwas still much more common in children than in adults. In theDutch health care system, general practitioners are the healthcare professionals that patients, including children, consult firstand from whom patients need to be referred to obtain specialistcare.'6 Therefore, they are good sources of information forstudying morbidity in a general population.MethodData were analysed from the Dutch national survey of morbidityand interventions in general practice, carried out by theNetherlands Institute for Primary Health Care (NIVEL) in 1987and 1988.'7 These data had been obtained from a randomlyselected, non-proportionally stratified sample of 161 generalpractitioners in 103 practices, drawn from all registered Dutchgeneral practitioners. Stratification took place to include a bal-ance of practices across all regions of the Netherlands, and ofrural and urban practices. The total practice population consistedof 332 303 patients, census data for whom had been recorded inadvance.The general practitioners were divided into four groups ofapproximately 40 each. Each group registered every contactbetween patient and practice during three months consecutively.The four registration periods were April-June, July-September,and October-December in 1987 and January-March in 1988, sothat one whole year was covered and possible seasonal variationscould be detected. The contacts were recorded on a speciallydesigned contact registration form, on which were noted reasonsfor encounter, diagnoses and associated interventions. Reasonsfor encounter and diagnoses were subsequently coded, in accord-ance with a modified version of the International classificationofprimary care.The national survey was based on an episode-oriented registra-tion of morbidity, which meant that different consultations con-cerning the same health problem were linked to one episode ofcare. This enabled an accurate estimate of the incidence becauseprovisional diagnoses were crystallized out into ultimate dia-gnoses. In the analysis only episodes in which the last diagnosisof the episode was molluscum contagiosum (ICPC subcode num-ber S76.2) were considered.In calculating incidence rates, the number of new episodes wasBritish Journal of General Practice, September 1994 417S Koning, M Bruijnzeels, L van Suijlekom-Smit and J van der Woudenused, the first consultation of which had taken place within theregistration period. This number was divided by the total numberof person years, that is, the period during which the patients werewithin the age group at risk multiplied by the number of patients.The probability of a child visiting the general practitioner formolluscum contagiosum at least once before the age of 15 years,was calculated by conversion of the age-specific incidence ratesinto the cumulative incidence at age 15 years. The underlyingassumption was that incidence rates are constant over timewithin each age category.'8Whenever possible, a distinction was made between venerealand non-venereal infection, by interpreting the registered local-ization of the lesions or the differential diagnosis.ResultsThere were 236 episodes of molluscum contagiosum in the studyyear, of which 202 were new episodes. There were 271 consulta-tion for the condition, thus the majority of episodes consisted ofjust one contact. Female patients accounted for 97 of the 202new episodes (48.0%) and male patients for 105 (52.0%).The number of new episodes and incidence in each age groupare shown in Table 1. The majority of cases were recordedbetween the ages of six and 10 years. The difference in incidencebetween males and females was not statistically significant. Thisequal distribution among sexes was the same in any age group.The cumulative incidence up to the age of 14 years was 168 per1000 children. This indicates that one out of six Dutch childrenaged 15 years have visited their doctor for molluscum conta-giosum at least once in their life.Eleven of 202 new episodes (5.4%) were recorded in patientsaged 15 years and over, of which at least two and at most six canbe considered to be the venereal form. This means that sexuallytransmitted molluscum contagiosum accounted for 1%-3% of allcases of molluscum contagiosum.The incidence rates of molluscum contagiosum, by season,region, and degree of urbanization, are shown in Table 2. Ofthese three characteristics, region was the most distinguishingfactor.Forty one practices had made no diagnoses of molluscum con-tagiosum while 21 practices had each diagnosed one case (incid-ence of 1.4 per 1000 person years). Two or three cases had beendiagnosed in 24 practices (2.8 per 1000 person years) and 17Table 1. Incidence of molluscum contagiosum, by age.No. of IncidenceAge (years) new episodes (per 1000 person years)0 0 01 7 6.22 16 15.23 10 9.54 8 7.75 15 14.46 24 22.87 22 21.18 25 24.49 19 18.810 25 25.011 7 6.812 6 5.813 3 2.714 4 3.315-24 7 0.5>24 4 0.1Total 202 2.4Original papersTable 2. Incidence of molluscum contagiosum by season, regionand degree of urbanization.Incidence (per 1000 person years)SeasonApril-June 2.8July-September 1.9October-December 1.8January-March 3.3RegionNortha 1.0Southb 2.7Centrec 3.2Urbanization (population)<30 000 2.330 000-50 000 2.5>50 000 2.68Groningen, Friesland and Drenthe. bNoord-Brabant and Limburg. CAllother provinces.practices had each diagnosed four or more cases (incidence of5.7 per 1000 person years). Of the four practices that hadrecorded 58 cases altogether, three were situated in the centraland one in the southern region.DiscussionThe differential diagnosis of molluscum contagiosum includeskeratoacanthoma, viral warts, granuloma and basal cell carcin-oma. However, the condition is considered to be easily recogniz-able,5'6'8 especially when multiple lesions are present. In thepresent study, diagnoses were usually made on clinical grounds,laboratory tests not being performed.In a literature search, two brief reports on the incidence ofmolluscum contagiosum in general practice were found: in alarge general practice in Belfast, Steele found four cases ofmolluscum contagiosum out of 2409 consultations,'4 which rep-resented 2% of all dermatological cases. In the Hague, theNetherlands, Relyveld and colleagues found an incidence of fourper 1000 patients per year, with a peak incidence between theages of five and nine years.15 Having been carried out in a bigcity, this study is not representative of rural areas; however, itsresult is comparable with the present findings.No cases in children aged less than one year were observed inthe study, which is in accordance with the international literature.This may reflect a passive immunity against the molluscum con-tagiosum virus that infants have obtained by maternal antibodies,or may indicate a long incubation period.'0The hypothesis that in general practice the paediatric type ismore common than the venereal type of molluscum conta-giosum, is strongly supported by the results: only between oneand three per cent of the cases were of the venereal type. Thereare some limitations on the importance of this finding. First, thegeneral practitioner may not recognize the genital pearly papulesas molluscs. Secondly, a number of patients may be absent fromthese data because in the case of venereal disease, a Dutchpatient can attend an outpatient department for sexually transmit-ted diseases directly without the need for prior referral from thegeneral practitioner. No reliable incidence rates can be obtainedfrom these clinics as molluscum contagiosum is not a reportabledisease. The number of missing patients can be estimated to besmall because the expected number of cases of venereal mollus-cum contagiosum occurring in the study population is 2.5 (calcu-lated from the incidence per 100 000 of the population derivedfrom English sexually transmitted disease clinics in 198219)British Journal of General Practice, September 1994418S Koning, M Bruijnzeels, L van Suijlekom-Smit and J van der Wouden Original paperswhich is not higher than the actual number of two to six seen inthe present study. That some dermatologists see relatively morecases of the venereal form than general practitioners might beexplained by the probability that adults with molluscum conta-giosum are more likely to be referred than children, and becauseof patients' direct attendance at outpatient departments for sexu-ally transmitted diseases.Several studies have associated molluscum contagiosum withvarious non-sexual modes of transmission: wrestling,20 swim-ming,'0"3 intra-familial spread,9"10 and sharing of towels.2Cultural differences may thus contribute to reported differencesin incidence rates, peak ages, and sex distributions betweencountries. The finding that the incidence and prevalence inwarmer climates are higher, and peak incidence is at a youngerage than in cooler climates, is consistent in all studies. The peakincidence at ages six to 10 years found here is comparable withthat of ages 10 to 12 years found in Scotland,'0 eight years inJapan,'3 and a mean age of six years in Alaska,9 all in contrastwith peak incidences at ages two to four years in Fiji, NewGuinea and Congo.'0"2'22 The common explanation is that inthese warmer countries transmission of the infection is facilitatedby the moist conditions that are favourable to the virus,2' as wellas by the lightweight clothes and consequent easy skin-to-skincontact.6 The finding that in the Netherlands the disease wasencountered most in winter seems to be contradictory to thisview. However, one has to consider the incubation period of theinfection, which is not known precisely: estimates vary betweentwo weeks and six months.6 Assuming the longer incubationperiod to be correct would make this seasonal trend in incidenceunderstandable.The equal sex ratio found in the present study is in contrast tothat in studies from Japan, Alaska and Fiji, where boys wereaffected more often.9"0"3 However, neither in New Guinea, norin the Hague,'2"15 were sex differences found. The most probableexplanation is that between different countries and years, habitsthat are associated with the spread of the infection, such as swim-ming, are different for each sex.The threefold difference in regional incidence is particularlystriking, as neither climatic nor cultural differences between thethree regions in the Netherlands play a considerable role. Animportant demographic feature of the northern region, its rela-tively low population density, cannot be the cause, because thedegree of urbanization is not correlated with incidence. It may bethat the skew in distribution of cases among practices broughtabout this result. In the past, several reports have been publishedon the occurrence of molluscum contagiosum in epidemics.9'20'23A few small epidemics of molluscum contagiosum may thushave caused the major regional differences in incidence foundhere.This is the first study on the epidemiology of molluscum con-tagiosum in a large, national general practice population.Because molluscum contagiosum is not common, significant dataon its incidence are difficult to obtain from small or local studypopulations. The main conclusions of this study are that the incid-ence of molluscum contagiosum in the Netherlands is 2.4 per1000 person years, with a peak incidence between the ages of sixand 10 years; the disease affects both sexes equally. Molluscumcontagiosum is a mainly paediatric disease, the sexually trans-mitted form is uncommon. The incidence is higher betweenJanuary and June than between July to December. Cases areunequally distributed among practices, possibly caused by smallepidemics.References1. Cobbold RJC, MacDonald A. Molluscum contagiosum as a sexuallytransmitted disease. Practitioner 1970; 204: 416-419.2. Becker TM, Blount JH, Douglas J, Judson FN. Trends in molluscumcontagiosum in the United States, 1966-1983. Sex Transm Dis 1986;13: 88-92.3. Oriel JD. The increase in molluscum contagiosum. BMJ 1987; 294:74.4. Cotton DWK, Cooper C, Barrett DF, et al. Severe atypicalmolluscum contagiosum infection in an immunocompromised host.Br J Dermatol 1987; 116: 871-876.5. Epstein WL. Molluscum contagiosum. Semin Dermatol 1992; 11:184-189.6. Highet AS, Kurtz J. Molluscum contagiosum. In: Champion RH,Burton JL, Ebling FJG (eds). Textbook ofdermatology. Oxford:Blackwell Scientific, 1992.7. Schwartz JJ, Myskowski PL. Molluscum contagiosum in patientswith human immunodeficiency virus infection. JAm Acad Dermatol1992; 27: 583-588.8. Douglas JM. Molluscum contagiosum. In: Holmes KK, Mardh P-A,Sparling PF, Wiesner PJ (eds). Sexually transmitted diseases. NewYork, NY: McGraw-Hill, 1990.9. Overfield TM, Brody JA. An epidemiologic study of molluscumcontagiosum in Anchorage, Alaska. J Pediatr 1966; 4: 640-642.10. Postlethwaite R, Watt JA, Hawley TG, et al. Features of molluscumcontagiosum in the north-east of Scotland and in Fijian villagesettlements. J Hygiene 1967; 65: 281-291.11. Hawley TG. The natural history of mollumscum contagiosum inFijian children. J Hygiene 1970; 68: 631-632.12. Sturt RJ, Muller HK, Francis GD. Molluscum contagiosum invillages of the West Sepik district of New Guinea. Med J Aust 1971;2: 751-754.13. Niizeki K, Kano 0, Kondo Y. An epidemic study of molluscumcontagiosum. Relationship to swimming. Dermatologica 1984; 169:197-198.14. Steele K. Primary dermatological care in general practice. JR CollGen Pract 1984; 34: 22-23.15. Relyveld J, Bergink AH, Nijhuis HGJ. Epidemiologische notities.Ulcus cruris, wratten en sterfsituatie. Huisarts en Wetenschap 1988;31: 266-267.16. Boerma WGW, de Jong FAJM, Mulder PH. Health care and generalpractice across Europe. Utrecht, Netherlands: NIVEL, 1993.17. Foets M, van der Velden J, de Bakker D. Dutch national survey ofgeneral practice. A summary of the survey design. Utrecht,Netherlands: NIVEL, 1992.18. Kleinbaum DG, Kupper LL, Morgenstern H. Epidemiologicresearch. Belmont, CA: Wadsworth, 1982: 106-108.19. Department of Health and Social Security. Sexually transmitteddiseases. Extract from the annual report of the Chief Medical Officerof the Department of Health and Social Security for the year 1983.Genitourin Med 1985; 61: 204-207.20. Low RC. Molluscum contagiosum. Edinburgh Med J 1946; 53:657-659.21. Brown ST, Nalley JF, Kraus SJ. Molluscum contagiosum. SexTransm Dis 1981; 8: 227-234.22. Torfs M, Lambelin G. Considerations sur le molluscum contagiosumen milieu tropical. Ann Soc Belg Med Trop 1959; 39: 703-709.23. Murray MJ, Murray AB, Murray NJ, et al. Molluscum contagiosumand herpes simplex in Maasai pastoralists; refeeding activation ofvirus infection following famine? Trans R Soc Trop Med Hyg 1980;74: 371-374.AcknowledgementWe wish to thank J van der Velden of the Netherlands Institute of PrimaryHealth Care.Address for correspondenceDr J C van der Wouden, Department of General Practice, ErasmusUniversity, PO Box 1738, 3000 DR Rotterdam, Netherlands.ALL MEMBERS PLEASE NOTEFellows, Members and Associates of The Royal College of GeneralPractitioners may claim a 10% reduction when booking classifiedadvertisements in the Journal.The Journal is your publication - why not take advantage of thespecial terms.COURSESPARTNERSHIPSASSISTANTSHIPSTRAINEES, etc.All enquiries to: Maria Phantis, RCGP, 14 Princes Gate, Hyde Park,London SW7 1PU, Tel: 071 581 3232 Ext. 261.British Journal of General Practice, September 1994 419

Molluscum contagiosum in Dutch general practice

Abstract

Similar works

Full text

Available Versions

Erasmus University Digital Repository