Nipah Outbreak

The bat-borne Nipah outbreak in Kerala has infected six people — two of whom have died — since it emerged in late August. Approximately 700 people, including healthcare workers, have been tested for infection over the past week.

Experts are concerned that increased human spread of the virus will make it more contagious, despite the fact that such outbreaks normally affect a small geographic area.

Nipah virus is another zoonotic virus that can spread from animals to humans. Fruit bats, which are predominantly found in the Nilgiris, are known to be the virus’ reservoirs.

The worrying factor

The Director General of the Indian Council of Medical Research (ICMR), Dr. Rajiv Bahl, gave critical insights into the Nipah virus, emphasising its high fatality rate and contrasting transmission characteristics with Covid-19.

Dr. Bahl emphasised that the Nipah virus, which is spread through respiratory droplets, has a high death rate ranging from 40% to 70%. “The most concerning aspect is that Nipah is 70-80 times deadlier than SARS-CoV-2, with a far higher death rate. In recent years, Malaysia had a mortality rate of 30 to 40% and Bangladesh had a rate of more than 70%.

In 2018, there were 23 occurrences in Kerala, with only two individuals surviving (a 91% fatality rate),” says Dr G V Rao, Director & Chief of Gastrointestinal & Minimally Invasive Surgery, Asian Institute of Gastroenterology.

Transmission to humans

Human infection results from spillover transmission from bats or through human-to-human transmission.

“Spillover transmission from bats can occur through two mechanisms: direct bat-to-human transmission (interaction with bats or their secretions, intake of raw date palm sap [tari] contaminated by bat saliva), or indirect transmission from bats via an intermediary animal host,” says Dr G V Rao.

“Human-to-human transmission was also essential in the 2004 outbreak in Bangladesh, when 33 of 36 confirmed cases had prior close contact with another infected patient. The median incubation period for Nipah virus infection caused by exposure to an infected patient was nine days (range, 6 to 11 days),” says  Dr K Subba Reddy,   Critical Care Specialist at Apollo Health City.

In this most recent outbreak in Kerala, one of the deaths occurred in a healthcare worker who treated a person sick with the virus.

Signs & symptoms

“When the  virus does cause disease, the most common symptom is encephalitis (brain swelling). Patients develop a fever and a severe headache, and many report disorientation, sleepiness, and confusion. Some patients acquire a chest infection as well with a high fatality rate. However, some people may continue to be asymptomatic,” says Dr G V Rao adding, “Typically, symptoms start to show four to fourteen days following exposure.”

According to the Centers for Disease Control and Prevention (CDC), it can be challenging to identify the virus in its early stages because its symptoms are similar to those of numerous other disorders. Severe symptoms from the virus might include confusion, sleepiness, seizures, or encephalitis, which is an infection of the brain. The CDC states that these can develop into a coma in 24 to 48 hours.

Fever
Headache
Myalgia
Dizziness
Altered consciousness
Acute encephalitis
Atypical pneumonia
Severe respiratory distress
Seizures

Diagnosis

The presence of virus in body fluids (e.g., throat and nasal swabs, tissue samples, urine, blood, and cerebrospinal fluid) is required for a definite diagnosis of Nipah virus infection.

“Because Nipah virus is designated as a biosafety category 4 agent, virus isolation is not commonly performed. As a result, other techniques, such as polymerase chain reaction (PCR) or serology, are increasingly routinely used,” says Dr Subba Reddy.

Treatment

Since the Nipah virus cannot be specifically treated with medications, medical care is only “supportive”, that is, it focuses on treating the patient’s specific symptoms and keeping them comfortable until they eventually recover.

“The core of treatment is supportive care, and infected patients may require intensive care monitoring. Mechanical ventilation for airway protection should be started as soon as neurologic impairment occurs. To date, the only successful post-exposure therapy against Nipah has been a human monoclonal antibody (mAb)-m102.4. The vaccinations are being developed, and we hope to have them ready for general public use soon,” says Dr Subba Reddy.

Prevention

Should be advised to avoid raw palm sap that has been polluted in order to reduce the risk of bat-to-human transmission, albeit this can be difficult and requires sensitivity to local norms and beliefs.

Should use gloves and other protective clothes while handling sick animals or their tissues, and they should avoid close unprotected personal contact with patients infected with the Nipah virus.

Health care personnel who care for patients who have a suspected or proven infection, or who handle their specimens, should use conventional infection control measures, as well as contact and droplet precautions.

“The Nipah virus, which is spread through respiratory droplets, has a high death rate ranging from 40% to 70.” — Dr Rajiv Bahl, Director General of the Indian Council of Medical Research (ICMR)

The most concerning aspect is that Nipah is 70-80 times deadlier than SARS-CoV-2, with a far higher death rate. In recent years, Malaysia had a mortality rate of 30 to 40% and Bangladesh had a rate of more than 70%. In 2018, there were 23 occurrences in Kerala, with only two individuals surviving (a 91% fatality rate).”  — Dr G V Rao, Director & Chief of Gastrointestinal & Minimally Invasive Surgery, Asian Institute of Gastroenterology.

The core of treatment is supportive care, and infected patients may require intensive care monitoring. Mechanical ventilation for airway protection should be started as soon as neurologic impairment occurs. To date, the only successful post-exposure therapy against Nipah has been a human monoclonal antibody (mAb)-m102.4. The vaccinations are being developed, and we hope to have them ready for general public use soon.” — Dr Subba Reddy, Critical Care Specialist at Apollo Health City.