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Dr Gérald Kierzek (Medical Director of Doctissimo)
Following the death of a teenager and several suspected cases, India is ramping up efforts to contain an outbreak of the dreaded Nipah virus. What do we know about the virus? What real threat does it pose?
The Nipah virus can be transmitted to humans by an animal (bats, pigs, etc.) or by contaminated food. It is a zoonotic virus. But it can also be transmitted from one human to another. Even if the outbreaks have not been significant or numerous so far, this virus is worrying in more than one way.
“It can infect a wide range of animal species and causes serious illness and death in humans, making it a public health concern.“, the World Health Organization (WHO) already reported in its 2018 report. It had already included the Nipah virus among the priority diseases on which scientific and medical research should focus.
What are the symptoms ?
According to WHO, the clinical picture of the Nipah virus can be symptomatic or asymptomatic. The incubation period is said to be 4 to 14 days and in the most serious cases 45 days. Most often, initially, infected people present the following symptoms:
- Fever ;
- Headaches;
- Muscle pain;
- Vomitings ;
- Sore throat.
Other signs may then appear:
- Dizziness ;
- Drowsiness;
- Altered state of consciousness;
- Atypical pneumonia;
- Acute respiratory failure;
In the most severe cases, brain infection (encephalitis) and convulsions that can lead to coma within 48 hours have been reported. The fatality rate is between 40% and 75%.
“As always with these viral infections, the initial symptoms of infection are non-specific and the disease is often not suspected at the time of consultation.” explains Dr. Gérald Kierzek, emergency physician and medical director of Doctissimo. “No tests are therefore carried out and therefore the real cases are probably more numerous, distorting all the data and in particular the overestimated lethality rate.“.
Most patients who survive acute encephalitis recover completely, but long-term neurological problems have been reported among survivors. About 1 in 5 patients have neurological sequelae, such as seizure disorders and personality changes. In a small number of cases, recovered individuals subsequently suffer a relapse or late-onset encephalitis.
Nipah virus was first detected in Malaysia in 1999 among pig farmers, WHO said. There have been no further cases since that cluster in the country. Several outbreaks have also occurred in Bangladesh since 2001, and in India as well.
Regarding the outbreaks in Malaysia and Singapore, WHO states that “Most human infections have resulted from a direct contact with sick pigs or their contaminated tissuesTransmission is thought to have occurred through contact with pig secretions or tissues from a sick animal.“. For those that occurred later in Bangladesh, the probable source of infection was the consumption of fruit or fruit juice contaminated with the urine or saliva of infected bats.
In September 2023, the Indian Ministry of Health had confirmed the existence of six cases of people affected by the virus, two of whom died. A strict health protocol, with identification of contact cases, closure of schools, etc., helped prevent a spread. According to WHOthis was the 6th outbreak of Nipah virus infection in India since 2001.
This positive case and the death of a teenager in July 2024 triggered an investigation by Indian authorities who identified 214 contact cases, including 60 at high risk.
The state of Kerala, which is experiencing rapid urbanization and sees deforestation and “cohabitation” of animals and humans, provides an environment favorable to the circulation of the virus between species.
As for contagion between humans, the rare studies suggest possible contamination via close contact with the secretions or excretions of a patient who is positive for the virus.
According to WHO: “Other regions may be at risk, as serological evidence of infection has been demonstrated in the known natural reservoir of Nipah virus (Pteropus species bats) and among several other bat species in many countries, including Cambodia, Ghana, Indonesia, Madagascar, the Philippines and Thailand.“.
What is the treatement ?
Currently there is no specific treatment or vaccine for Nipah virus. Management is limited to supportive care to treat respiratory and neurological complications.
Nipah virus: could it cause a new pandemic?
The Asian origin of the virus may be reminiscent of Covid-19. However, there are several differences.
On the one hand, the Nipah virus has been known for more than 20 years and epidemics have remained very localized.
“The risk of international transmission could mainly be linked to fruits or fruit-based products (raw date juice, etc.) potentially contaminated by the urine or saliva of infected bats.” “says Dr. Kierzek.”But simple measures like washing or peeling fruit are effective. So far, there is little risk of a new pandemic from this virus.“.
Of course, the situation in India must be monitored, but it is reasonable to assume that this virus will not cause a new pandemic. Until now, no cases have ever been recorded in Europe.
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