Abstract
BackgroundHuman cases of highly pathogenic avian influenza A (H5N1) virus infection continue to occur in Southeast Asia. The objective of this study was to identify when and where human H5N1 cases have occurred in Vietnam and how the situation has changed from the beginning of the H5N1 outbreaks in 2003 through 2014, to assist with implementing methods of targeted disease management.MethodsWe assessed the disease clustering and seasonal variation of human H5N1 cases in Vietnam to evaluate the geographical and monthly timing trends. The clustering of H5N1 cases and associated mortality were examined over three time periods: the outbreak period (2003–2005), the post-outbreak (2006–2009), and the recent period (2010–2014) using the flexibly shaped space-time scan statistic. The most likely cases to co-cluster and the elevated risks for incidence and mortality were assessed via calculation of the relative risk (RR). The H5N1 case seasonal variation was analysed as the cyclic trend in incidence data using Roger’s statistical test.ResultsBetween 2003 and 2005, H5N1 cases (RR: 2.15, p = 0.001) and mortality (RR: 2.49, p = 0.021) were significantly clustered in northern Vietnam. After 2010, H5N1 cases tended to occur on the border with Cambodia in the south, while H5N1 mortality clustered significantly in the Mekong delta area (RR: 6.62, p = 0.002). A significant seasonal variation was observed (p < 0.001), with a higher incidence of morbidity in December through April.ConclusionsThese findings indicate that clinical preparedness for H5N1 in Vietnam needs to be strengthened in southern Vietnam in December–April.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1391-8) contains supplementary material, which is available to authorized users.
Highlights
Human cases of highly pathogenic avian influenza A (H5N1) virus infection continue to occur in Southeast Asia
The aims of the present study were to use space-time analyses to evaluate when and where human H5N1 cases have occurred in Vietnam and how the situation has changed from the beginning of the H5N1 outbreaks in 2003 to the present
Human cases of avian influenza H5N1 infection in Vietnam Between December 2003 and December 2014, a total of 127 confirmed human H5N1 cases were reported to the World Health Organization (WHO) from Vietnam, 64 of which were fatal [1]
Summary
Human cases of highly pathogenic avian influenza A (H5N1) virus infection continue to occur in Southeast Asia. The objective of this study was to identify when and where human H5N1 cases have occurred in Vietnam and how the situation has changed from the beginning of the H5N1 outbreaks in 2003 through 2014, to assist with implementing methods of targeted disease management. In Southeast Asia, including in Vietnam, human cases of highly pathogenic avian influenza A (H5N1) virus infection continue to occur and have been associated with high mortality rates [1]. Previous studies indicate that early diagnosis and administration of antiviral agents relate to patient survival [7,8,9,10,11].
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