September 25, 2018
4 min read

‘Could have been much worse’: India stops deadly Nipah outbreak

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Experts credited a strong public health response with containing a deadly outbreak of Nipah virus in India in the same month that it began.

Nineteen patients were infected in the outbreak in the state of Kerala — most in the hospital — and 17 died, including at least one health care worker, officials said. Soon after the outbreak was reported to the National Center for Disease Control on May 19, India launched a coordinated response to contain the spread that included local, state and national health agencies. No new cases were reported after May 29.

Daniel R. Lucery

“It could have been much worse,” Daniel R. Lucey, MD, MPH, adjunct professor of medicine and infectious diseases at Georgetown University Medical Center and research associate in anthropology at the Smithsonian National Museum of Natural history, told Infectious Disease News. “The medical and public health response in Kerala prevented it from becoming much worse.”

The response

Indian researchers and officials presented findings from the outbreak at the CDC’s International Conference on Emerging Infectious Diseases in Atlanta.

The index patient, a male, was infected in the community. The remaining patients, including two family members of the index case, contracted the virus through human-to-human transmission in one of several hospitals, reported G Arunkumar, PhD, professor and head of the department of virus research at Manipal Academy of Higher Education, and colleagues.

The cause of the index patient’s infection remains unclear, although bats — the primary reservoir of Nipah — are assumed to be the source, according to Devendra T. Mourya, PhD, and colleagues from the National Institute of Virology and the Indian Council of Medical Research. Mourya and colleagues collected and tested 52 fruit bats in the affected area and found that 19% were positive for the virus — more than double the proportion described in past studies.

Nipah virus, which was discovered in 1999, is one of the world’s deadliest pathogens. It is on WHO’s list of priority diseases in urgent need of accelerated research and development, along with Ebola, Zika, Rift Valley fever and other, better known illnesses.

Humans are infected through direct exposure to bats carrying the virus — such as by drinking raw date palm sap that bats have urinated or defecated into, or consuming fruit that bats have partially eaten — or through contact with infected pigs or other people. The virus can cause encephalitis and pneumonia, Lucey said. There are no vaccines or effective treatments.


Compounding the danger of person-to-person spread, Lucey said the May outbreak occurred in an area of India — the southwest — where Nipah virus had never been seen. It was only the third Nipah virus outbreak reported in India, and the first since 2007. The previous two occurred in northeast India, near the border of Bangladesh, which experiences yearly outbreaks of Nipah, usually around February, Lucey said.

At the CDC conference, officials from the Indian National Center for Disease Control and the Directorate General of Health Services said they identified 2,649 contacts from the 19 confirmed cases and observed them for 21 days — “extremely impressive,” Lucey said. Fifteen suspected cases in six other states all tested negative.

According to the officials, multiple agencies collaborated to share data, rapidly trace contacts and implement infection prevention and control measures, including isolating patients. Lucey said he was impressed that it took just a matter of days to get an initial diagnosis of Nipah virus infection and have it confirmed in a national laboratory hundreds of miles away. Isolating Nipah as the cause of the illnesses was paramount to initiating the public health response.

“It was a big deal, but they were ready for it,” Lucey said. “The response was really exemplary in terms of identifying a pathogen new to that part of the country and successfully stopping the outbreak. It was very difficult to do, but they did it. ... We talk so much about preparedness, and this was a success for preparedness at the hospital level, the laboratory level, for local, regional and national health departments.”

‘Worrisome’ findings

Among the findings presented at the conference, Lucey was troubled that researchers found so many bats in the outbreak zone that tested positive for Nipah virus.

“It’s worrisome because it means that you should not only expect Nipah to come back in Kerala, but potentially in all of India,” he said.

In an article published in the International Journal of Infectious Diseases, Lucey and Georgetown medical student Halsie Donaldson, MS, argued that countries with no experience fighting Nipah should be better prepared to respond to large outbreaks of the virus in urban and rural settings to prevent a tragedy on the scale of the West African Ebola epidemic.

“To me [the Kerala outbreak] shows that we should be anticipating and planning for Nipah outbreaks in new locations, far away from where known outbreaks have occurred in the past, including other countries than India,” Lucey said. “Next time, who knows — maybe it’ll be Myanmar or the Philippines or Indonesia or Sri Lanka. Wherever Nipah virus-infected fruit bats fly, the infection can occur in humans. It’s a predictable event that we should be preparing for.” – by Gerard Gallagher

Disclosures: Lucey reports no relevant financial disclosures.