Nipah virus infection

Nipah virus infection is a serious zoonotic disease. A zoonotic disease is an illness that spreads from animals to humans. The Nipah virus (NiV) is an RNA virus within the genus Henipavirus. It normally circulates among fruit bats of the genus Pteropus. These bats carry the virus without appearing to get sick. This is likely because they have special immune systems to handle the stress of flying. The virus is significant because it can cause severe illness in humans.

The virus moves through several different transmission pathways. Initial human outbreaks are always zoonotic. This happens when humans are exposed to the contaminated secretions or tissues of infected bats or pigs. Once a human is infected, the virus can spread between people. This occurs through close contact with an infected person. It can also happen through exposure to infected body fluids like blood, urine, or nasal secretions. While most experts do not call it airborne, it can spread through short-range respiratory droplets. It can also spread indirectly via contaminated objects, known as fomites.

Symptoms of the infection vary depending on the person. Some people experience an asymptomatic infection, meaning they show no signs of being sick. Others develop an acute respiratory infection. This often feels like the flu, including fever, headache, myalgia, and vomiting. It can also cause coughing, a sore throat, and difficulty breathing. In severe cases, patients develop encephalitis. Encephalitis is a dangerous inflammation of the brain. This can lead to dizziness, drowsiness, altered consciousness, and seizures. Patients may fall into a coma within 24 to 48 hours. Some people also experience acute respiratory distress syndrome.

There are several specific risk factors for catching the virus. In Malaysia and Singapore, risk was high for those with close contact to infected pigs. In Bangladesh and India, the disease is often linked to eating fruit partially consumed by bats. It is also linked to drinking raw date palm sap, also called toddy. This sap can be contaminated by bat saliva or excreta. Using water from wells inhabited by bats is another risk. Healthcare workers and caretakers of infected patients are also at high risk.

Scientists first identified the virus in 1998. A research team at the University of Malaya found it during an outbreak in Malaysia. The virus was named after the Malaysian village of Sungai Nipah. At first, authorities thought the cause was Japanese encephalitis. This mistake delayed effective measures to stop the spread. In 1999, Malaysian authorities culled millions of pigs to stop the outbreak. Since then, many outbreaks have occurred in the "Nipah Belt." This region includes Malaysia, Singapore, India, and Bangladesh.

The impact of the virus is measured by its high mortality rate. The case fatality rate is estimated to be between 40% and 75%. For example, a 2001 outbreak in Siliguri, India, had a 74% mortality rate. In 2004, an outbreak in the Faridpur district of Bangladesh had a 75% mortality rate. Even survivors may face long-term neurological consequences. These include memory loss, impaired cognition, and personality changes. The virus can also lie dormant in survivors. It can reactivate many months or years later, which can lead to death.

Currently, there is no specific treatment or vaccine for Nipah virus. Management is restricted to supportive care. This includes providing rest, hydration, and treating specific symptoms. Some antivirals like Ribavirin, Acyclovir, and Remdesivir have been assessed, but their efficacy is not fully clear. However, there is progress in medical research. In January 2024, a candidate vaccine called ChAdOx1 NipahB began Phase I clinical trials. Prevention remains the best protection. This includes avoiding contact with bats and sick pigs and using strict hygiene in hospitals.