Abstract
ObjectiveIn March 2007, we investigated a cluster of Nipah encephalitis to identify risk factors for Nipah infection in Bangladesh.MethodsWe defined confirmed Nipah cases by the presence of IgM and IgG antibodies against Nipah virus in serum. Case-patients, who resided in the same village during the outbreak period but died before serum could be collected, were classified as probable cases.ResultsWe identified three confirmed and five probable Nipah cases. There was a single index case. Five of the secondary cases came in close physical contact to the index case when she was ill. Case-patients were more likely to have physical contact with the index case (71% cases versus 0% controls, p = <0.001). The index case, on her third day of illness, and all the subsequent cases attended the same religious gathering. For three probable cases including the index case, we could not identify any known risk factors for Nipah infection such as physical contact with Nipah case-patients, consumption of raw date palm juice, or contact with sick animals or fruit bats.ConclusionThough person-to-person transmission remains an important mode of transmission for Nipah infection, we could not confirm the source of infection for three of the probable Nipah case-patients. Continued surveillance and outbreak investigations will help better understand the transmission of Nipah virus and develop preventive strategies.
Highlights
Among the 122 Nipah cases identified between 2001 to 2007 in Bangladesh, 87 (71%) died and 62 (51%) developed illness following person to person transmission [1]
Though human-to-human transmission plays an important role in subsequent transmission of Nipah [2,3], in Bangladesh some of the identified routes of introduction of Nipah virus from its natural reservoir, Pteropus fruit bats, in to humans are though drinking of raw date palm sap contaminated by bats, contact with infected animals and possibly through direct contact with bat secretion[4]
Findings from outbreak investigations in Bangladesh demonstrate that family members, friends, relatives and neighbors who came in direct contact with infected respiratory and other body secretions of Nipah spreaders were significantly at greater risk of subsequently acquiring the infection [2,3]
Summary
Among the 122 Nipah cases identified between 2001 to 2007 in Bangladesh, 87 (71%) died and 62 (51%) developed illness following person to person transmission [1]. One of the distinct features of Nipah virus epidemiology in Bangladesh is that only certain case-patients apparently spread the disease to others. In a previous review of cases in Bangladesh, we identified only nine Nipah spreaders and each of them spread the disease to a mean of seven persons (range 1–22). All of the Nipah spreaders died [1]. Findings from outbreak investigations in Bangladesh demonstrate that family members, friends, relatives and neighbors who came in direct contact with infected respiratory and other body secretions of Nipah spreaders were significantly at greater risk of subsequently acquiring the infection [2,3]
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