Investigation of Dengue Infection in Asymptomatic Individuals during a Recent Outbreak in La Réunion

Olga de Santis (1, 2) , Emilie Pothin (3, 4) , Nicolas Bouscaren (1) , Seth Irish (3, 4) , Marie-Christine Jaffar-Bandjee (5) , Luce Menudier (6) , Julie Ramis (7) , Cédric Schultz (1) , Florence Lamaurt (1, 8) , Ania Wisniak (2) , Antoine Bertolotti (1, 5) , Sarah Hafsia (7) , Philippe Dussart (9) , Laurence Baril (9) , Patrick Mavingui (7) , Antoine Flahault (2)

1 CIC 1410 - Centre d'Investigation Clinique de La Réunion - INSERM
2 UNIGE - Université de Genève = University of Geneva
3 Swiss Tropical and Public Health Institute [Basel]
4 Unibas - Université de Bâle = University of Basel = Basel Universität
5 CHU La Réunion - Centre Hospitalier Universitaire de La Réunion
6 Santé publique France - French National Public Health Agency [Saint-Maurice, France]
7 PIMIT - Processus Infectieux en Milieu Insulaire Tropical
8 ISPED - Institut de Santé Publique, d'Epidémiologie et de Développement
9 Institut Pasteur de Madagascar

The number of dengue cases has increased dramatically over the past 20 years and is an important concern, particularly as the trends toward urbanization continue. While the majority of dengue cases are thought to be asymptomatic, it is unknown to what extent these contribute to transmission. A better understanding of their importance would help to guide control efforts. In 2019, a dengue outbreak in La Reunion resulted in more than 18,000 confirmed cases. Between October 2019 and August 2020, 19 clusters were investigated in the south, west, and east of the island, enabling the recruitment of 605 participants from 368 households within a 200 m radius of the home of the index cases (ICs). No active asymptomatic infections confirmed by RT-PCR were detected. Only 15% were possible asymptomatic dengue infections detected by the presence of anti-dengue IgM antibodies. Only 5.3% of the participants had a recent dengue infection confirmed by RT-PCR. Although the resurgence of dengue in La Réunion is very recent (2016), the rate of anti-dengue IgG positivity, a marker of past infections, was already high at 43% in this study. Dengue transmission was focal in time and space, as most cases were detected within a 100-m radius of the ICs, and within a time interval of less than 7 days between infections detected in a same cluster. No particular demographic or socio-cultural characteristics were associated with dengue infections. On the other hand, environmental risk factors such as type of housing or presence of rubbish in the streets were associated with dengue infections.

Mots clés: dengue; asymptomatic infections; La Réunion; cluster study; dengue outbreak

Domaines: Sciences du Vivant [q-bio]

Olga de Santis, Emilie Pothin, Nicolas Bouscaren, Seth Irish, Marie-Christine Jaffar-Bandjee, et al.. Investigation of Dengue Infection in Asymptomatic Individuals during a Recent Outbreak in La Réunion. Viruses, 2023, 15 (3), pp.742. ⟨10.3390/v15030742⟩. ⟨pasteur-04096793⟩