Less Infectious, But High Mortality Rate: Here's Why Nipah Has Kerala On Its Toes

Following the deaths of two individuals due to Nipah virus infection in northern Kozhikode district, Kerala authorities have swiftly implemented containment measures to halt the virus's spread. While Nipah is not considered as contagious as the novel coronavirus responsible for Covid-19, its high fatality rate and severe impact on patients raise significant concerns.

What Is the Nipah Virus?

Nipah is a zoonotic virus, originating in animals before infecting humans. It causes a severe respiratory infection and encephalitis, or brain fever, in humans. Named after the Malaysian village where it was first detected in 1998-99, Nipah has also affected Singapore.

The virus's natural host is believed to be fruit bats, known as flying foxes, from the Pteropodidae family. These bats commonly reside near "markets, places of worship, schools, and tourist spots" throughout South and Southeast Asia.

How Does the Disease Infect an Individual?

Nipah virus can spread through various means. It primarily infects humans when they consume fruits or drink raw date palm juice contaminated by an infected fruit bat's saliva or urine. Infections have also occurred among those who climb trees inhabited by bats.

Transmission via an intermediate host is another method, with the 1998-99 outbreak in Malaysia-Singapore believed to have originated from contact between humans and sick pigs or their contaminated tissues.

Direct transmission between infected and uninfected individuals through bodily fluids and secretions is also possible. It has been reported among family members and caregivers of infected patients, particularly those with respiratory issues.

What Are the Symptoms?

Nipah virus infection can cause mild to severe disease, including brain swelling (encephalitis) and potential death. Symptoms include fever, altered mental status, severe weakness, headache, respiratory distress, cough, vomiting, muscle pain, convulsions, and diarrhea.

The incubation period ranges from 4 to 14 days, during which an infected individual can unknowingly spread the virus to others.

How Infectious Is It, and How Fatal?

The Nipah virus has a limited infectiousness, with an average transmission rate of less than one person per infection. However, its high fatality rate, ranging from 40-75%, contributes to its containment.

The risk of the virus evolving into a more efficiently transmitted strain remains, which could lead to a devastating outbreak, given its high mortality rate.

How Is It Treated?

Currently, there are no specific drugs or vaccines for Nipah virus infection. Supportive care is recommended, including rest, hydration, and symptom treatment. Immunotherapeutic treatments such as monoclonal antibody therapies are under development for Nipah virus infections.

Ribavirin, an antiviral, may help reduce mortality among patients with Nipah virus-induced encephalitis.

What Steps Are Taken to Contain It?

Containment measures include isolation of affected areas, strict vigilance, contact tracing, and quarantine for those in close contact with infected individuals. Additionally, mask-wearing, surface sanitization, and other preventive measures are implemented.

How Is It Detected?

Nipah virus is detected through an RT-PCR test of body fluids, including throat and nasal swabs, cerebrospinal fluid, urine, and blood. Antibody tests can be conducted after symptom recession.

However, initial symptoms are nonspecific, making early diagnosis challenging and potentially delaying outbreak detection and response.

Where Have Nipah Outbreaks Been Reported, and How to Prevent It?

Local Nipah outbreaks have occurred in South and Southeast Asian countries, including Bangladesh, India, and Singapore. Other countries at risk due to local bat species carrying the virus include Cambodia, Ghana, Indonesia, Madagascar, the Philippines, and Thailand.

Preventive measures are similar to those for COVID-19 and include frequent handwashing, avoiding contact with infected individuals' blood or body fluids, and refraining from consuming raw date palm sap or fruits that may be contaminated by bats. Avoiding contact with sick bats or pigs and areas where bats roost is also recommended.