5 Monivong Boulevard, P.O Box. 983, Phnom Penh, Cambodia [email protected]

Dengue fever is a major public health problem in Cambodia (estimated 2010 pop. 14 million). All four dengue virus serotypes have circulated in the country during the past 5 years. Annual incidence of symptomatic dengue virus infection has been reported at 2 per 1000 for persons

Financial support

The Kampong Cham study was conducted in 2011 thanks to a research grant obtained from Namru-2. Denfree is made possible by a grant from EU-FP7.

Studies

Namru-2

In 2011, 29/40 (72.5%) cases of confirmed Dengue infections identified through systematic serosurveys around index cases said they had presented no symptoms.

In 2011, the Institut Pasteur du Cambodge (IPC) and the Dengue National Control Program with support from US Naval Medical Research Unit #2 (NAMRU-2) undertook a community-based prospective study for dengue in 14 villages in rural Kompong Cham province. The objective was to ascertain the proportion of asymptomatic dengue infections in a Cambodian rural community. Suspect (febrile) cases were tested by real-time RT-PCR, NS1 antigen detection kit, anti-DENV IgM and IgG serologies. Biologically-confirmed index cases were followed up by exhaustive household serosurveys within 200 meters around the index cases’ residence. Results: Between July 10 and 16 October 2011 (Monsoon), an average monthly population of 5,635 persons aged 6 months – 20 years agreed to be monitored weekly of which 1,365 presented fever and were tested for dengue. In all, 57 (4.2%) symptomatic dengue cases were identified by surveillance. One case developed fatal hemorrhagic dengue. In the investigations around 10 febrile index cases an additional 1,393 persons were tested for recent dengue infection. Among these, 40 cases were positive, of which 29 (72.5%) declared they had felt no symptoms. The overall symptomatic dengue attack rate was estimated at 12 per 1000 for the study period. Finally, one additional case of Japanese Encephalitis virus was identified. Analysis Is ongoing. Conclusion: Preliminary results show that dengue underreporting is high in Cambodia. Furthermore, the majority (72.5%) of biologically-confirmed cases in systematic household investigations remain asymptomatic. These data must be included in mathematical models to estimate vaccine coverage needs.

Publications

S. Ly, V. Duong, A. Rachmat, C. Yasuda, C. Ngan, R. Huy, S. Ong, W. Rogers, P. Buchy, A. Tarantola. Dengue attack rate and proportion of asymptomatic infections in the Kampong Cham prospective community study, 2011: preliminary data. Oral communication, Abstract 07.008. 15th ICID, Bangkok, Thailand, June 13-16, 2012.

DENFREE, a major Dengue study is under way, and SEAe will be implemented soon. Clinical research teams will be increasingly mobilized transversally in these projects.

For this research Dr. S. Ly was awarded the Novartis Vaccines Awards for Epidemiology of Infectious Diseases, 2012.

Denfree

With funding from EU-FP7, the Institut Pasteur du Cambodge is participating in an ambitious 3-year study. Samples from Cambodia will be analyzed and shared with an extensive network of world-renowned research laboratories to assess the various determinants associated with asymptomatic Dengue infection. To 03/10/2012, the DENFREE study has been conducted for over 3 months in the Kompong Cham study site (began on 24/06/2012). In all, 135 confirmed dengue cases in hospital and 12 confirmed dengue cases in the community have given rise to 86 completed investigations that include 52 single-house investigations (Index Case’s house only) and 34 multiple-house investigations (697 households). Nine investigations are still ongoing. In these 749 houses, we included 2,269 persons aged less than or equal to 40 years old who agreed to participate and 98 (4.3%) were tested positive for dengue by NS1 rapid test or by PCR. Of these tested participants, 82 (83.7%) presented symptomatic infection by DENV and 16 (0.7% of total, 16.3% of diagnosed dengue) presented asymptomatic infection to date.