If Kerala was taken by surprise last year by the first outbreak of Nipah virus infection, its recurrence this year strongly suggests that the virus is in circulation in fruit bats. After all, a study published on May 25 this year demonstrated that fruit bat was the source of the virus. In the absence of active surveillance for the virus in fruit bats, such outbreaks are going to become common.
A year after Kerala’s prompt action quickly brought the deadly Nipah virus infection outbreak under check in two districts (Kozhikode and Malappuram), the State has once again shown alacrity in dealing with a reported case.
A 23-year-old student admitted to a private hospital in Ernakulam on May 30 tested positive for the virus on June 4. But even as the government was awaiting confirmation from the National Institute of Virology (NIV) Pune, steps had been taken to prevent the spread of the disease by tracing the contacts, setting up isolation wards and public engagement.
Two health-care workers who had come in contact with the patient exhibited some symptoms and are being treated, and the infection is suspected in five more people. While 314 people who had come in close contact with the student are kept in isolation to prevent the spread of the disease, the numbers might be more — the student had reportedly travelled to four districts (Ernakulam, Thrissur, Kollam, and Idukki) recently.
Containing the spread of Nipah virus is important as the mortality rate was 89% last year, according to a May 5, 2019 paper in the journal Emerging Infectious Diseases. At the same time, subclinical manifestation in three people who had come in contact with the Nihap virus patient last year has also been documented. The source of infection in the index case (student) remains unknown. However, transmission to 18 contacts last year and the two health-care workers this year has been only through human-to-human route.
If Kerala was taken by surprise by the first outbreak last year, its recurrence this year strongly suggests that the virus is in circulation in fruit bats. After all, the virus isolated from four people and three fruit bats (Pteropus medius) last year from Kerala clearly indicated that the carrier of the Nipah virus which caused the outbreak was the fruit bat, according to a May 25, 2019 paper in the journal Emerging Infectious Diseases. Analysing the evolutionary relationships, the study found 99.7-100% similarity between the virus in humans and bats.
The confirmation of the source and the recurrence of Nipah virus infection outbreak this year strongly suggest that Kerala must be alert to the possibility of frequent outbreaks. Even in the absence of hard evidence of the source of the virus till a few days ago, fruit bats were widely believed to be the likely candidate. That being so and considering the very high mortality rate when infected with the virus, it is shocking that Kerala did not undertake continuous monitoring and surveillance for the virus in fruit bats.
One reason for the failure could be the absence of a public health protection agency, which the government has been in the process of formulating for over five years, to track such infective agents before they strike. Not only should Kerala get this agency up and running soon, it should also equip the Institute of Advanced Virology in Thiruvananthapuram to undertake testing of dangerous pathogens such as the Nipah virus.
Known for very high health indicators in the country, Kerala cannot lag behind in dangerous infectious diseases front.