Country Report on Dengue Fever/Dengue Haemorrhagic Fever and Japanese Encephalitis in Lao People\u27s Democratic Republic

The Lao People\u27s Democratic Republic (P. D. R.) a landlocked country located in Indochina, with a population of 4.2 million and land area of 146.8 thousand square kilometers, density=16/km^2. More than 90 percent of the population relies on farming and the activities of these people depend on the climate condition. The country as a whole is subject to the monsoon which imposes a rainy season from May to September and dry season from October to April. Annual rainfall varies from 1300mm to 3000mm depending on exposure to the southwest monsoon. Agricultural system, breeding of swine and climate condition are favorable to develop the vectors of dengue fever/dengue haemorrhagic fever (DF/DHF) and Japanese encephalitis (JE). However, the occurrence of haemorrhagic complication led to epidemic proportion and to significant morbidity, especially among children. Fatal haemorrhagic complications are usually confined to persons under 15 years of age with a peak incidence in the 3-6 years age group

Varicella zoster and fever rash surveillance in Lao People’s Democratic Republic

Background In Lao PDR, the epidemiology of varicella infection is uncertain, since it is not a notifiable disease and VZV outbreaks are rarely reported as fever/rash (F/R) diseases. Methods We estimated the seroprevalence of VZV (IgG ELISA) in different age cohorts (9 months to 46 years; N = 3139) and investigated VZV and 6 other viruses in patients during F/R outbreaks and in an ad hoc sentinel site in the context of the national reporting system (IgM ELISA, PCR). Results At least 80% of the sampled population had evidence of VZV infection before the age of 15. The largest increase in seroprevalence occurred between the age groups 1 to 5 and 6 to 7 year-olds. A VZV outbreak (clade 2) also occurred in this age group mostly during the first year of primary school (median age 6 years, interquartile range 4.0–7.5). During a dengue outbreak, 6% had varicella. At our F/R sentinel site, 14% of children with viral etiology were laboratory diagnosed as varicella and among others, a sizeable number of measles (N = 12) and rubella cases (N = 25) was detected compared to those reported for the whole country (N = 56 and 45), highlighting nationwide a large challenge of underreporting or misdiagnosis of these notifiable diseases because of lack of diagnostic laboratory capacity. Conclusion We recommend strengthening the clinical and laboratory diagnosis of VZV, measles and rubella, the surveillance and reporting of notifiable F/R diseases by retraining of healthcare workers and by setting up sentinel sites and enhancing laboratory capacity

Low seroprevalence of COVID-19 in Lao PDR, late 2020

Background In 2020 Lao PDR had low reported COVID-19 cases but it was unclear whether this masked silent transmission. A seroprevalence study was done August - September 2020 to determine SARS-CoV-2 exposure. Methods Participants were from the general community (n=2433) or healthcare workers (n=666) in five provinces and bat/wildlife contacts (n=74) were from Vientiane province. ELISAs detected anti- SARS-CoV-2 Nucleoprotein (N; n=3173 tested) and Spike (S; n=1417 tested) antibodies. Double-positive samples were checked by IgM/IgG rapid tests. Controls were confirmed COVID-19 cases (n=15) and pre-COVID-19 samples (n=265). Seroprevalence for the general community was weighted to account for complex survey sample design, age and sex. Findings In pre-COVID-19 samples, 5·3%, [95% CI=3·1-8·7%] were anti-N antibody single-positive and 1·1% [0·3-3·5%] were anti-S antibody single positive. None were double positive. Anti-N and anti-S antibodies were detected in 5·2% [4·2-6·5%] and 2·1% [1·1-3·9%] of the general community, 2·0% [1·1-3·3%] and 1·4% [0·5-3·7%] of healthcare workers and 20·3% [12·6-31·0%] and 6·8% [2·8-15·3%] of bat/wildlife contacts. 0·1% [0·02-0·3%] were double positive for anti-N and anti-S antibodies (rapid test negative). Interpretation We find no evidence for significant SARS-CoV-2 circulation in Lao PDR before September 2020. This likely results from early decisive measures taken by the government, social behavior, and low population density. High anti-N /low anti-S seroprevalence in bat/wildlife contacts may indicate exposure to cross-reactive animal coronaviruses with threat of emerging novel viruses. Funding Agence Française de Développement. Additional; Institut Pasteur du Laos, Institute Pasteur, Paris and Luxembourg Ministry of Foreign and European Affairs (“PaReCIDS II”)

Causes of non-malarial fever in Laos: a prospective study

Background Because of reductions in the incidence of Plasmodium falciparum malaria in Laos, identifi cation of the causes of fever in people without malaria, and discussion of the best empirical treatment options, are urgently needed. We aimed to identify the causes of non-malarial acute fever in patients in rural Laos. Methods For this prospective study, we recruited 1938 febrile patients, between May, 2008, and December, 2010, at Luang Namtha provincial hospital in northwest Laos (n=1390), and between September, 2008, and December, 2010, at Salavan provincial hospital in southern Laos (n=548). Eligible participants were aged 5–49 years with fever (≥38°C) lasting 8 days or less and were eligible for malaria testing by national guidelines. Findings With conservative defi nitions of cause, we assigned 799 (41%) patients a diagnosis. With exclusion of infl uenza, the top fi ve diagnoses when only one aetiological agent per patient was identifi ed were dengue (156 [8%] of 1927 patients), scrub typhus (122 [7%] of 1871), Japanese encephalitis virus (112 [6%] of 1924), leptospirosis (109 [6%] of 1934), and bacteraemia (43 [2%] of 1938). 115 (32%) of 358 patients at Luang Namtha hospital tested infl uenza PCR-positive between June and December, 2010, of which infl uenza B was the most frequently detected strain (n=121 [87%]). Disease frequency diff ered signifi cantly between the two sites: Japanese encephalitis virus infection (p=0·04), typhoid (p=0·006), and leptospirosis (p=0·001) were more common at Luang Namtha, whereas dengue and malaria were more common at Salavan (all p<0·0001). With use of evidence from southeast Asia when possible, we estimated that azithromycin, doxycycline, ceftriaxone, and ofl oxacin would have had signifi cant effi cacy for 258 (13%), 240 (12%), 154 (8%), and 41 (2%) of patients, respectively. Interpretation Our fi ndings suggest that a wide range of treatable or preventable pathogens are implicated in nonmalarial febrile illness in Laos. Empirical treatment with doxycycline for patients with undiff erentiated fever and negative rapid diagnostic tests for malaria and dengue could be an appropriate strategy for rural health workers in Laos. Funding Wellcome Trust, WHO–Western Pacifi c Region, Foundation for Innovative New Diagnostics, US Centers for Disease Control and Prevention

Emergence of chikungunya in Moonlapamok and Khong Districts, Champassak Province, the Lao People’s Democratic Republic, May to September 2012

Introduction: Chikungunya is a vector-borne disease transmitted to humans by Aedes mosquitoes, which are widespread in the Lao People’s Democratic Republic. However, chikungunya virus (CHIKV) had not been detected in the country before outbreaks reported in July 2012. The first outbreaks were detected through health care worker event-based surveillance. Methods: The case definition for the outbreaks was defined as a person with acute onset of fever (> 38 °C) and severe arthralgia (joint pain) or arthritis from 1 May 2012 in Champassak Province. Rapid response teams conducted active case finding, performed an environmental assessment including an entomological survey and implemented control measures. Descriptive analysis was undertaken in Microsoft Excel. Results: There were 197 cases (attack rate 3.4%) of suspected chikungunya reported from 10 villages in Moonlapamok and Khong Districts of Champassak Province. All age groups (age range: seven months–74 years) were affected with slightly more female (56%) than male cases. Thirty-one per cent (16 of 52) of serum samples tested positive for CHIKV by polymerase chain reaction. The environmental assessment found poor water storage practices and high entomological indices. Discussion: These outbreaks show the effectiveness of health care worker event-based surveillance and the importance of sharing of information across borders for detecting emerging diseases. Public health education is an important measure to prevent epidemics of chikungunya. Information about chikungunya should be supplied to health care workers in the region so they are alert to the potential spread and are able to implement control measures for this disease

Varicella zoster and fever rash surveillance in Lao People’s Democratic Republic

Abstract Background In Lao PDR, the epidemiology of varicella infection is uncertain, since it is not a notifiable disease and VZV outbreaks are rarely reported as fever/rash (F/R) diseases. Methods We estimated the seroprevalence of VZV (IgG ELISA) in different age cohorts (9 months to 46 years; N = 3139) and investigated VZV and 6 other viruses in patients during F/R outbreaks and in an ad hoc sentinel site in the context of the national reporting system (IgM ELISA, PCR). Results At least 80% of the sampled population had evidence of VZV infection before the age of 15. The largest increase in seroprevalence occurred between the age groups 1 to 5 and 6 to 7 year-olds. A VZV outbreak (clade 2) also occurred in this age group mostly during the first year of primary school (median age 6 years, interquartile range 4.0–7.5). During a dengue outbreak, 6% had varicella. At our F/R sentinel site, 14% of children with viral etiology were laboratory diagnosed as varicella and among others, a sizeable number of measles (N = 12) and rubella cases (N = 25) was detected compared to those reported for the whole country (N = 56 and 45), highlighting nationwide a large challenge of underreporting or misdiagnosis of these notifiable diseases because of lack of diagnostic laboratory capacity. Conclusion We recommend strengthening the clinical and laboratory diagnosis of VZV, measles and rubella, the surveillance and reporting of notifiable F/R diseases by retraining of healthcare workers and by setting up sentinel sites and enhancing laboratory capacity

Chronic hepatitis B prevalence among children and mothers: results from a nationwide, population-based survey in Lao People's Democratic Republic.

BACKGROUND: Hepatitis B is regarded as a serious public health issue in Lao People's Democratic Republic (Lao PDR), a Southeast Asian country. However, disease epidemiology among the general population is not well known, and thus a nationwide cross-sectional survey for hepatitis B surface antigen (HBsAg) prevalence in children and their mothers was conducted. METHODS AND FINDINGS: We applied three-stage cluster sampling using probability proportionate to size. After randomly selecting child (5 to 9 years old) and mother (15 to 45 years old) pairs from the selected villages, questionnaires and HBsAg rapid tests were conducted. Data from 965 child and mother pairs were analyzed. Multivariate logistic regression analyses were used to investigate the independent association of individual background characteristics for the odds of being HBsAg positive. In total, 17 children and 27 mothers were HBsAg positive. HBsAg prevalence was estimated to be 1.7% (95% confidence interval: 0.8%-2.6%) in children, and 2.9% (95% confidence interval: 1.7%-4.2%) in their mothers after taking sampling design and weight of each sample into account. Mother's infection status was positively associated with HBsAg positivity in children (p<0.001), whereas other potential risk factors, such as ethnicity, proximity to health centers, and history of surgery, were not. There were no significant associations between mother's HBsAg status and history of surgery, and other sociodemographic factors. CONCLUSIONS: Despite the slow implementation of the hepatitis B vaccination program, HBsAg prevalence among children and their mothers was not high in Lao PDR compared to reports from neighboring countries. The reasons for the differences in prevalence among these countries are unclear. We recommend that prevalence surveys be conducted in populations born before and after the implementation of a hepatitis B vaccination program to better understand the epidemiology of hepatitis B