Nipah virus (NiV) infection is a newly emerging disease that can cause severe problems in both animals and humans. The natural host of Nipah virus are fruit bats of the Pteropodidae Family, Pteropus genus.
Nipah (NiV) was first identified during an outbreak of disease that took place in Kampung Sungai Nipah, Malaysia in 1998. Pigs were found to be the intermediate hosts in this outbreak. But, in subsequent NiV outbreaks, there were no intermediate hosts. It was then found in Bangladesh in 2004, when humans became infected with Nipah virus as a result of consuming date palm sap that was contaminated by infected fruit bats.
Human-to-human transmission of Nipah virus has also been documented. A case of human to human transmission has been recording in a hospital setting in India among others.
In the Bangladesh and India outbreaks, consumption of fruits or fruit products (such as raw date palm or their juices juice) contaminated with urine or saliva from infected fruit bats was the most common source of infection.
There are cases where some level of human to human transmission of NiV has also been reported among family and care givers of infected patients.
As found in the outbreaks in Bangladesh and India, Nipah virus spread directly from human-to-human through close contact with people's secretions and excretions.
Transmission of Nipah virus can occur in the following ways:
Infections in humans may range from asymptomatic infection to acute respiratory infection and fatal encephalitis. Commonly observed initial signs and symptoms of Nipah virus infection are similar to influence, such as:
Later, the infected person may develop these symptoms:
Initial signs and symptoms of the infection are not specific and usually the infection is not suspected. This often creates challenges in diagnosing the infection and preventing outbreaks.
NiV infection can be diagnosed by studying clinical history. The tests that are often used include real time polymerase chain reaction (RT-PCR) from bodily fluids and as antibody detection via ELISA. Other tests for the diagnosis of Nipah virus infection are:
Currently, there is no drug or vaccine to cure Nipah virus infection even though this is a priority disease, identified by WHO. Major complications that occur in the severe cases involve respiratory and neurologic complications, which are usually managed with intensive supportive care.
The drug ribavirin has been shown to be effective against the viruses in vitro, but human investigations to date have not been conclusive and the clinical usefulness of ribavirin is not confirmed.
Passive immunization using a human monoclonal antibody targeting the Nipah G glycoprotein has been studied in the post-exposure therapy in the ferret model and found to be of benefit.
Since there is no licensed vaccine for the infection, the only way to reduce the risk of infection in people is by raising awareness of the risk factors and educating people about the measures that can be taken to reduce an exposure to the Nipah virus and decrease the chances of spread of the infection.
These are important considerations to help prevent the infection:
Reducing the risk of animal-to-human transmission
Reducing the risk of human-to-human transmission
The incubation period is defined as time interval from infection to the onset of symptoms. In case of Nipah virus infection, the incubation period is considered between from 4-14 days. However an incubation period as long as 45 days has been reported in some cases.
Most people who survive acute encephalitis are able to fully recover. But there are cases where long term neurologic conditions have been reported in survivors of the infection.
According to data obtained from WHO, approximately 20% of patients are left with residual neurological consequences such as seizure disorder and personality changes. A small number of people who recover subsequently relapse or develop delayed onset encephalitis.
Fatality rate is estimated about 40% to 75%; however. Latent infections with subsequent reactivation of Nipah virus and death can occur months and sometimes even years after the exposure.