Less infectious but more fatality than COVID: Experts on Nipah virus

Amid the outbreak of Nipah virus in Kerala, the health experts have cautioned that the virus carries a higher mortality rate but it is weak in its ability to spread from person-to-person. The mortality rate is high in Nipah virus cases compared to Covid-19 cases. As per the health expert, Nipah typically only spreads to close and personal contacts, unlike Covid that can easily spread through the air.

“What sets Nipah apart from other viruses is its high mortality rate, which means the chance of death if a person developed symptomatic infection from this virus. The mortality of Covid on average is below 1%, even though in certain sub groups it is worse. The problem with COVID however is its ability to spread quickly across the globe, affecting massive numbers of people”, said Dr Rajeev Jayadevan, Co Chairman, National IMA COVID Task Force.

“This was the reason for such a large death toll despite a relatively low individual mortality rate for COVID. While the high mortality rate of Nipah might sound alarming, what offers some solace is the fact that this virus is weak in its ability to spread from person-to-person. In other words, most Nipah outbreaks are small and self-limiting”, said Dr Jayadevan.

Earlier, the Indian Council of Medical Research (ICMR) Director General Rajiv Bahl said, “If Covid had a mortality of 2-3 percent, here the mortality is 40-70 percent. So, the mortality rate is extremely high”.

During the 2018 Nipah outbreak in Kerala, a mortality of 91% was recorded, and the most recent Nipah outbreak from Bangladesh yielded a mortality of 73%. The basic Reproduction number R0 or R-zero for Nipah virus is only 0.4, which means that if one person is infected with Nipah virus, on average, the person can spread it only to 0.4 people, said Dr Jayadevan.

Explaining further, if 10 people pick up Nipah virus infection, collectively, they can only spread it to 4 people, and these four people can only spread it to 2 and so on. Thus, the numbers become progressively small and eventually the outbreak dies down.

“In contrast, during the first year of the pandemic, COVID virus had an R-zero of 2 to 3, which meant that one person with Covid could pass it on to 3 people and those three people could pass it on to 9 and then 27 and so on. That is indeed how Covid, which started in one person somewhere in China in 2019, rapidly spread around the world and is continuing to do so”, added Dr Jayadevan.

Nipah is a different category of virus. It lives peacefully in bats, but under some mysterious and unknown circumstance, jumps to human beings, the exact mode of which has not been proven yet. However, the speculations include consumption of fruit or food or beverages contaminated with saliva, reproductive or excretory material of the bat carrying the virus, or direct interaction with bats which might have gone unreported or undetected, said Dr Jayadevan, advising to avoid all contact with bats.