Interview: ‘Genome sequencing research needed to understand Nipah variants’
Kerala witnessed an outbreak of the Nipah Virus (NiV), a highly pathogenic RNA virus for the fourth time in September 2023. The state went through similar scares in 2018, 2019 and 2021 which warranted emergency responses. The natural host of Nipah virus are fruit bats that belong to the Pteropodidae family and that are in the Pteropus genus. Such bats, also called flying foxes, are found in South and South East Asia.
According to researchers, seven to eight months in a year are critical for Nipah infections in Kerala. These bats mate during August to November, births might occur from May to mid-July and these are months with higher possibility of virus shed. Dr Suma Krishnasastry, Professor, Internal Medicine, MCH Alappuzha, trained by the World Health Organisation on Tropical Disease Research, was a part of a team assigned for Nipah virus research by the Kerala government in 2018 and to prepare a report. She speaks to TNM on her observations.
Do we know the exact source of Nipah infections in Kerala?
Yes, we know the source. As of now Nipah virus human infections in Kerala have spread through fruit bats. In 2018, studies by Kerala Veterinary and Animal Sciences University, National Institute of Virology and the National Institute of Epidemiology, a medical research organisation based in Chennai, had carried out studies on bats across all districts of Kerala.
It was found that virus load was higher in the Kozhikode bats. Usually during their reproductive period, which starts from the month of May, there are chances of bats shedding the virus in high amounts. Also this is the fruiting season in Kerala. Any secretion from bats with high virus loads has the potential to infect humans. We cannot completely avoid the presence of bats. Habitat destruction is not a solution. Also there will be genetic variations in the virus present in them. The problem here is not that we did not identify the source, we have identified it, but we cannot wipe out their habitat. It is not specific to Kerala. In Bangladesh there were many episodes, now they are effectively containing it. Here also we are able to identify it in the first stage and contain it effectively. We have a strong surveillance system.
Was the 2018 outbreak a lesson for Kerala?
In 2018, Nipah infections spread to 19 people and only two among them survived. The delays in detection was the reason for the spread as it was the first time. It took a few days to diagnose what it was. The next time it happened we were cautious and were able to contain it sooner. Now we know that isolation is the first step to be taken. Containment will be easier now.
What are the symptoms seen in Nipah patients?
There are two kinds of disease manifestations. The first is encephalitis, which affects the brain, where one can get seizures, fever, loss of consciousness etc… In this condition the caretakers closely monitor patients which could result in easy spread of infection. The second type is primarily respiratory. Here respiratory failure, depletion of oxygen levels, Respiratory Distress Syndrome etc.. can occur. In 2018, the majority of the patients had encephalitis. But in later stages they all developed respiratory symptoms. Both these conditions together cause death. The 2019 patient in Ernakulam mainly had neurological encephalitis symptoms. Two manifestations are equally fatal. These differences in symptoms cannot be because of differences in variants, since the same patient is getting both symptoms. It may be because of the virus load. But there can be differences in each episode due to variants. We can find out more about it only by doing genome sequencing. It's better to have more research in this area. Fatality is dependent on the symptoms. In 2018 most of the deaths happened within four or five days with the onset of symptoms.
How are the patients treated?
We have no treatment other than to provide best support care. But Monoclonal antibodies can be tried. We had with us m102.4, a monoclonal antibody, in 2018 and in 2019. There are many procedures to try the medicine and training was given to professionals to administer the medicine. But we haven´t yet used it as either the patients got well or died. We can use that only after the virus is confirmed. If the patient's condition is progressing it can´t be used. If the patient situation is worse and under ventilator support there is no use for the medicine. We can try the medicine within 3 to 4 days of the onset of symptoms.
How can Nipah infections be prevented?
The primary factor is precaution. The behaviour pattern of people should change. People in regions where Nipah infections have occurred before should be extra careful to avoid contact with bats. They should not touch or consume half bitten fruits. Don't touch bats. Initially there were reports that an index patient in Kozhikode had touched a baby bat. I am not sure whether it was true. But people should be extra careful. They shouldn't spit publicly, should cover their mouth and nose while sneezing or coughing and make these habits part of their daily life. They should report immediately at nearby health centres if they have any symptoms.