In February 2024 WHO reported that two laboratory-confirmed cases of Nipah virus (NiV) infection have been identified from the Dhaka division of Bangladesh since the start of the year. Outbreaks of NiV are seasonal in Bangladesh; cases usually occur between December and April as date palm sap is harvested and consumed. Since the first case was reported in 2001, human infections have been recorded “almost every year” with a case fatality rate of between 25% (2009) and 92% (2005).
The overall risk at national levels is described as “moderate”, which considers the disease severity, limitation of treatment, shared natural habitat of bats and zoonotic transmission partners, and the lack of licensed vaccines against NiV infection.
Two cases
On 30th January and 7th February 2024, the Bangladesh National Focal Point (NFP) for the International Health Regulations (IHR) notified WHO of two “epidemiologically unlinked cases” of NiV. The first was a 38-year-old male from Manikganj district, who developed a fever followed by respiratory distress, restlessness, and insomnia on 11th January. He was admitted to a local hospital on 16th January before being transferred to the intensive care unit of a hospital in Dhaka City on 18th January.
On 21st January, blood and throat samples were collected and the patient tested positive (RT-PCR and ELISA) for NiV. After being transferred to another hospital in Dhaka city on 27th January, the patient died on 28th January. WHO states that he had a “history of consuming raw date palm sap”. After extensive contact tracing, 91 contacts were identified but none tested positive by PCR or ELISA.
The second case was a three-year-old female from Shariatpur district. She was taken to a healthcare facility on 30th January after two days of fever, altered consciousnesses, and seizures. She was diagnosed with encephalitis and shock and was transferred to the isolation ward of a hospital in Dhaka city. Blood and throat samples were collected on 30th January and tested positive the following day, when the patient died. WHO notes that this case also had a “history of regularly consuming fresh raw date palm sap”. On 7th February contact tracing found no other positive cases.
NiV transmission and presentation
NiV is a bat-borne zoonotic disease that is transmitted through infected animals or contaminated food. It can also be transmitted from person to person, but this is “less common”. The incubation period usually ranges from 4 to 14 days, although a previous incubation period of up to 45 days has been reported.
Infection can cause a “range of clinical presentation” such as acute respiratory infection and fatal encephalitis. The case fatality rates depend on local capabilities for early detection and clinical management, particularly because there are no licensed vaccines or therapeutics.
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