Urban Epidemic of Dengue Virus Serotype 3 Infection, Senegal, 2009

Ousmane Faye, Yamar Ba, Oumar Faye, Cheikh Talla, Diawo Diallo, Rubing Chen, Mireille Mondo, Rouguiétou Ba, Edgard Macondo, Tidiane Siby, Scott C. Weaver, Mawlouth Diallo, and Amadou Alpha Sall

Author affiliations: Institut Pasteur, Dakar, Senegal (Ousmane Faye, Y. Ba, Oumar Faye, C. Talla, D. Diallo, M. Mondo, R. Ba, M. Diallo, A.A. Sall); University of Texas Medical Branch, Galveston, Texas, USA (R. Chen, S.C. Weaver); Laboratoire de Biologie Médicale BIO24, Dakar (E. Macondo, T. Siby)

Abstract

An urban epidemic of dengue in Senegal during 2009 affected 196 persons and included 5 cases of dengue hemorrhagic fever and 1 fatal case of dengue shock syndrome. Dengue virus serotype 3 was identified from all patients, and Aedes aegypti mosquitoes were identified as the primary vector of the virus.

Dengue is an arboviral disease transmitted by Aedes spp. mosquitoes and caused by 4 serotypes of dengue virus (DENV): DENV-1, DENV-2, DENV-3, and DENV-4. DENV belongs to the family Flaviviridae, genus Flavivirus (1). More than 2.5 billion persons worldwide are considered at risk for dengue (2); the number of dengue infections per year has been estimated at 390 million, although only 96 million are symptomatic (3).

Figure 1

Thumbnail of Geographic distribution of patients with confirmed dengue in the region of Dakar, Senegal. Number of patients is shown in parentheses. Inset shows location of Dakar in Senegal and in Africa.

Figure 1. . Geographic distribution of patients with confirmed dengue in the region of Dakar, Senegal. Number of patients is shown in parentheses. Inset shows location of Dakar in Senegal and in Africa....

Most dengue infections occur in urban areas in tropical and subtropical regions, but imported cases have been reported in nontropical regions. During October 2009, imported DENV-3 infections were diagnosed in Turin, Italy (4), and Marseille, France (5), from patients returning from the Louga and Thies regions in Senegal (Figure 1). DENV-specific IgM and/or RNA were also detected in 5 persons living in Dakar, Senegal, who were suspected to have dengue. We report results from investigation of the 2009 dengue epidemic in Senegal.

The Study

During October 2009–January 2010, a total of 696 serum samples were collected from persons in Senegal who were suspected to have dengue. A suspected dengue case was defined as fever and>2 of the following: myalgia, arthralgia, headache, and rash. Most samples were collected in Dakar (n = 606) and Thies (n = 87) (Table, Appendix). In Dakar, samples were collected from 9 neighborhoods: Plateau (n = 202), Almadies (n = 157), Grand Dakar (n = 117), Parcelles Assainies (n = 82), Pikine (n = 13), Guediawaye (n = 15), Niayes (n = 5), Thiaroye (n = 10), and Rufisque (n = 5) (Figure 1). Samples were tested by real-time reverse transcription PCR and ELISA for virus genome and IgM, respectively.