Infection with the Nipah virus has killed at least 10 people out of 12 confirmed cases in Kozhikode and Malappuram of Kerala. While underlining the dangers of the disease, which has a high mortality rate, experts stress that there is no reason to panic because outbreaks, usually caused by fruit bats, have been generally localised. Teams rushed to Kerala by the Centre are working to contain the outbreak.
Containment is key
There is no need to panic, said Dr D T Mourya, director, National Institute of Virology (NIV). Virologists working on the ground say the outbreak has been localised and early diagnosis has helped contain the first wave. Although the outbreak has raised fears of travellers spreading the virus beyond Kerala, scientists have pointed out that it is a rare infection, traditionally localised.
The reservoir for the virus is fruit bats, which roost on trees and rarely come into contact with humans. Less than 1% of bats will be infected with the virus and rarely will they infect humans, experts say. Bats can infect pigs, too, another way the disease can spread to humans. Infected humans can spread it to others they come in contact with. During a 1998-99 outbreak in Malaysia, Nipah virus antibodies were also detected in dogs, cats, goats and horses that had been exposed to infected pigs.
Containment vs treatment
Timely laboratory confirmation and aggressive epidemiologic tracing of contacts with patient quarantine and isolation can contain spread of the virus. This is important because there is no effective specific treatment for the infection. Treatment is symptomatic and supportive. Severely ill individuals need to be hospitalised and may require intensive care. Because Nipah virus encephalitis can be transmitted person-to-person, standard infection control practices and proper barrier nursing techniques are important.
The disease has a very high mortality rate, which is the reason for the rush to contain it. In the previous two outbreaks in India, both in West Bengal, there were 42 deaths out of 72 cases in Siliguri in 2001, and five deaths out of 30 who showed the symptoms in Nadia in 2007.
Where it came from
Genetic studies on the Bengal outbreak suggested a relation to the Bangladesh strain of the virus. Consumption of raw date palm sap contaminated by bats was the primary source. Strong evidence indicated human-to-human transmission, Dr Mourya said.
How did the virus reach Kerala? “Extensive studies will be required at field and laboratory levels before we can make a comment,” an NIV scientist said. Human cases have been reported from only Bangladesh, India, Malaysia and Singapore; fruit bats are present in many other countries.
The classical form is an acute and rapidly progressive encephalitis with or without respiratory involvement. Nipah encephalitis comes with 3-14 days of fever and headache, followed by drowsiness, disorientation and mental confusion, Dr Mourya said. Acute encephalitis progresses to coma within 24-48 hours. Symptoms include non-productive cough during the early part of the disease.