Nipah virus (NiV) infection is a new emerging zoonotic disease (transmissible from animals to humans) affecting both animals (pigs and other domestic animals) and humans. Fruit bats of the Pteropodidae Family, Pteropus genus are the natural host for the virus.
NiV was first identified in Malaysia in 1998, during an outbreak of disease that occurred in a place called Kampung Sungai Nipah. Pigs were the intermediate hosts in this outbreak and most of the human cases resulted from exposure to ill pigs. After that in Singapore during March 1999 eleven abattoir workers developed NiV infection following close contact with imported pigs from Malaysia.
Outbreak of Nipah virus infection was reported in Bangladesh in 2001. Since then, outbreaks of Nipah virus encephalitis have been reported almost every year in selected districts of Bangladesh. Consumption of raw date palm sap contaminated by flying bats was the primary source of human NiV infection in Bangladesh.
In India outbreaks of NiV infection were reported from Siliguri (January-February 2001) and Nadia (April-2007) districts in West Bengal. Seventy one cases with 50 deaths (70% of the cases) occurred in two outbreaks. Recently in May 2018 an outbreak of NiV infection is reported from the state of Kerala.
Outbreaks reported from South-East Asia have a seasonal pattern with occurrence during winter and spring (December-May). This pattern could be associated with several factors like the breeding season of the bats, increased shedding of virus by the bats and the date palm sap harvesting season. Nipah cases may occur in a cluster or as an outbreak.
There is strong evidence that loss of natural habitats of bats by human activity may attribute to emergence of bat-related viral infection communicable to humans and animals.
Symptoms of disease may appear with in 5 to 14 days (incubation period) after an exposure to infection:
Clinical presentations of NiV infection in humans varies from asymptomatic infection to fever, headache for 3-14 days followed by drowsiness, respiratory illness, disorientation and mental confusion.
In severe cases these signs and symptoms can progress to coma within 24-48 hours.
The case fatality rate ranges from 9 to 75%.
Those who may have recovered from an acute episode may also have a relapse.
Long-term sequelae following Nipah virus infection have been noted in the form of persistent convulsions and personality changes.
Latent infections with subsequent reactivation of Nipah virus and death have also been reported months and even years after exposure
Nipah virus (NiV) infection is caused by a virus, that is named after the Malaysian village where it was first discovered. NiV is a member of the family Paramyxoviridae, genus Henipavirus.
Mode of transmission-
Fruit bats of the genus Pteropus have been identified as natural reservoirs of NiV. Bats are symptomless carriers of NiV, but infected bats shed virus in their excretion and secretion such as saliva, urine, semen and excreta. The NiV is highly contagious among pigs and spreads by coughing.
Transmission of disease can occur-
After direct contact with infected bats, infected pigs.
Human to human transmission by direct contact from other NiV infected people.
By consumption of raw date palm sap and fruits contaminated with infectious bat excretions.
Laboratory confirmation of NiV Infection in a suspected case of NiV can be done during the acute and convalescent phases of the disease by using a combination of tests.
Virus isolation attempts and real time polymerase chain reaction (RT-PCR) from throat and nasal swabs, cerebrospinal fluid, urine, and blood can be performed in the early stages of disease.
Antibody detection by ELISA (IgG and IgM) can be used in later stages.
In fatal cases (after death), immunohistochemistry on tissues collected during autopsy may be the only way to confirm a diagnosis.
There is no effective treatment for NiV disease, Intensive supportive care is the primary treatment for human cases, though use of an antiviral medication (ribavarin ) may reduce the symptoms of nausea, vomiting, and convulsions.
Treatment is mostly focused on managing fever and neurological symptoms. Severely ill individuals may require the use of a ventilator.
A vaccine is being developed.
Nipah virus infection can be prevented by-
Avoiding exposure to sick pigs and bats in endemic areas.
Not drinking raw date palm sap.
Early detection of disease in communities and livestock, and raising awareness of transmission and symptoms of disease.
Reinforcing standard infection control practices to avoid human-to-human infections in hospital settings (nosocomial infection) – Healthcare workers caring for patients with suspected or confirmed NiV should implement Standard Precautions when caring for patients and handling specimens from them.