THIRUVANANTHAPURAM: Nipah virus (NiV) is a zoonotic virus that can be transmitted to humans from animals directly or through contaminated food. Fruit bats (Pteropus bat species) are the natural reservoirs of NiV, but the exact mechanism of transmission from bats to humans remains largely unknown and the transmission of the virus from bats to humans is considered a rare event.
The most common way for humans to become infected with NiV is through contact with the bodily fluids of infected bats or pigs. For instance, people who eat a fruit contaminated with bat urine or saliva are at risk of infection.
The risk of transmission via fruits or fruit products (such as raw date palm juice) contaminated with urine or saliva from infected fruit bats can be prevented by washing them thoroughly and peeling them before consumption. Fruit with signs of bat bites should be discarded.
A survey by the ICMR- National Institute of Virology revealed that fruit bats with NiV antibodies are found in Kerala, Tamil Nadu, Karnataka, Goa, Maharashtra, Bihar, West Bengal, Assam, Meghalaya and Puducherry. The Nipah virus was first identified in 1999 during an outbreak among pig farmers in Malaysia. The first NiV outbreak in India was reported in February 2001 from Siliguri in West Bengal. Later, Kerala reported Nipah outbreaks in 2018, 2019, 2021 and recently in 2023.
Despite Kerala’s well-coordinated health system response to contain the outbreak, the NiV continues to confound experts. In contrast to cases in Malaysia and Bangladesh, where evidence of animal-human interaction exists, Kerala’s recurrent outbreaks lack similar documentation. The strain of NiV in Kerala is believed to have originated in Bangladesh and exhibits relatively lower infectivity (with an R0 value of 0.4) but significantly higher mortality rates (ranging from 40% to 75%).
Health experts say that patients suffering from the virus become contagious when they are severely ill. Dr Althaf A, epidemiologist and a professor at Government Medical College in Thiruvananthapuram, who conducted extensive studies on the Nipah outbreak in the state in 2018, said, “Individuals who interact with such patients without adequate precautions are at risk of infection during this stage.”
Infection
Direct contact with infected animal/human, eating fruits or food items contaminated by the infected animal
Symptoms
Mild symptoms- Fever, Headache, Cough, Sore throat, Difficulty breathing, Vomiting.
Severe symptoms: Disorientation, drowsiness, or confusion, Seizures, Coma, Brain swelling (encephalitis)
Incubation period: 4-14 days
Diagnosis: RT-PCR of throat and nasal swabs, samples of cerebrospinal fluid, urine and blood
Treatment: No treatment, but symptoms can be treated and supportive care can be provided
First Nipah outbreak in India
February 2001
Siliguri in West Bengal, 66 cases, 45 deaths
Nipah in Kerala
May 2018 - Kozhikode, Malappuram. 23 cases, 21 deaths
May 2019 - Kochi, 1 case, 0 deaths
September 2021- Kozhikode, 1 case, 1 death
September 2023 - Kozhikode, 6 cases, 2 deaths (Till September 18)
