First evidence of circulation of chikungunya virus in Mozambique

Background: Chikungunya virus (CHIKV) is a emerging arbovirus that caused a large outbreak in the south western Indian Ocean Islands and Mozambique Channel in 2005-2007 and since then is spreading, causing several outbreaks in areas not previously affected. Although several of the affected countries are in the close proximity of Mozambique, no previous study has yet been conducted to investigate the circulation of this virus in Mozambique. Methods & Materials: Acute febrile patients with no evident cause of fever attending a health centre in a suburban area of Maputo city in Mozambique between January and September 2013 were consecutively enrolled. Study area is characterized by poverty, poor sanitation, high prevalence of malaria and households are precarious. Main source of income is informal sector. Paired acute and convalescent samples were requested from each participant. Convalescent samples were initially screened for IgG anti-CHIKV using commercial indirect immunofluorescence test (IIFT) (EUROIMMUN AG, Lüebeck, Germany) and if positive, the corresponding acute sample was screened using the same test. Results: Four hundred forty two patients were enrolled, but only 274 (61.9%) returned to the convalescent visit. The median age of study participants was 27.0 years and 59% (249/242) was female. Out of 46 (16.8%) convalescent samples were positive for IgG anti-CHIKV. The corresponding acute samples were also screened for IgG anti-CHKV and out of these, 5 were negative, suggesting a seroconversion rate of 2.0%. Four-fold titre rise of IgG anti-CHIKV was confirmed for 7 samples. Most of the positive samples clustered around August and September. Conclusion: This report represents the first evidence of circulation of CHIKV in Mozambique. Seroconversion rate and titre rise of IgG anti-CHIKV strongly suggest that CHIKV is circulating in Mozambique, causing acute infection in suburban area of Maputo city. As a next step, all samples suggestive of acute infection by CHIKV will be screened using IIFT IgM anti-CHIKV in order to confirm acute infection and attempt to isolate the virus in cell culture is ongoing. We recommend that further studies should be conducted to investigate if CHIKV is causing sporadic cases, unsuspected outbreaks or if it has become an endemic virus.