It has been confirmed that ten people have lost their lives to Nipah virus in India in northern Kerala districts of Kozhikode and Malappuram. Two more people who were suspected to have contracted the virus have died but it has not been confirmed that it was due to Nipah. 116 people who had come in contact with some of the infected persons have been quarantined and are under observation. Meanwhile, two people have been suspected with Nipah virus from Mangalore in Karnataka.
Given India’s density, transmission can be fast. Our public health systems are not equipped to deal with a virus for which there is neither preventive vaccine nor a definite cure. Moreover without proper information rumours can abound and panic may spread fast. So what do we know about Nipah virus so far and what are its implications for India?
According to the WHO, Nipah virus (NiV) is a newly emerging zoonosis that causes severe disease in both animals and humans. Fruit bats of the Pteropodidae Family, Pteropus genus are the natural host of the virus but it has been found in many other species, especially domestic pigs and domestic cats, dogs, goats, horses, and sheep.
NiV was first identified in Malaysia in 1998-9 during an outbreak of the disease and gets its name from the village in Malaysia where the person, from whom the virus was first isolated, succumbed to the disease. While the disease is spread through fruit bats or ‘flying foxes’ the first incidence of NiV occurred when pigs in Malaysian farms came in contact with the bats who had lost their habitat due to deforestation.
This may not be the first outbreak in India. According to the CDC (Centre for Disease Control), in the same year, although retrospectively, another outbreak was identified in Siliguri, India. Since 1999 while no outbreaks have been reported in Malaysia or Singapore, outbreaks occur almost annually in Bangladesh and have also been reported several times in India.
In Kerala, three people died from the same family and fourth is undergoing treatment. Dead bats were found in the well of their family’s home. Human to human transmission is also possible and thus hospital workers taking care of patients are also at risk. A young nurse, a mother of two, succumbed to the disease while taking care of the patients.
Symptoms of NiV include fever, headache, drowsiness, mental confusion, coma, encephalitis, and death. The incubation is a period of 5-14 days and illness generally presents with 3-14 days of fever and headache followed by disorientation and other serious signs. The fatality rate of the disease is high, and is estimated to be 75%. Also, there is no specific treatment or a preventable vaccine for NiV apart from intensive supportive care.
Preventive measures thus become extremely important. First is the control of bats, and preventing animals from eating fruit contaminated by bats, or consumption of date palm sap, including toddy, that has been contaminated. Health care workers, doctors, and nurses taking care of patients should take precautions like washing hands, wearing gloves, cap mask and gown. Exposure to sick pigs must also be avoided. In extreme cases, pigs have been killed to prevent the spread further.
CDC recommends more research in this area; particularly with respect to better understand the ecology of the bats and NiV and investigation of the disease within the reproductive cycle of bats. Better surveillance tools include laboratory assays for early detection of disease in communities and livestock.
Currently, two million people live in areas inhabited by the Pteropus bat reservoir and are thus susceptible to NiV. Vaccine development is thus much desired. The good news is that there is strong evidence that protective vaccine is feasible. However, due to the extreme lethal nature of NiV, producing a safe, live attenuated vaccine with no potential of reversion is considered difficult. The most promising vaccine candidate is a subunit vaccine consisting of a soluble glycoprotein from the related henipavirus Hendra virus (HeV), which causes human and equine disease. The bad news is that no clinical trials have yet begun for NiV vaccine candidates. The epidemiology and sporadic nature of NiV outbreaks makes large scale, Phase III clinical trials difficult to plan to assure achieving meaningful efficacy results that would support licensure.
Till now NiV is not a global threat. However, as WHO and CDC point out, any virus is just a flight away from anywhere. Also, a high population density nation like India is particularly susceptible. Moreover, the public health system in India is poor, symptoms are often not reported early to doctors, and surveillance and monitoring facilities, while good and quite adept in this particular outbreak, are lacking for a population this size. India has been quite vigilant in this particular instance. Nevertheless, a joint effort by Health Ministry, frontline health workers and hospital workers, laboratory technicians and scientists, and even researchers for vaccine development can ensure that an outbreak doesn’t become an epidemic.
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