A 52-year-old man in Kerala’s Palakkad district was the victim of a new deadly Nipah virus infection on July 12, making it the tenth case of the disease’s spillover (transmission from animals to people) in the southern Indian state since 2018.
This year alone, Kerala has reported four Nipah cases, including two deaths, all within a 50km (30-mile) radius, on the border of the Malappuram and Palakkad districts.
675 people are being watched in five districts across the state, keeping things high on the alert.
What are the symptoms of the Nipah virus, what are its symptoms, and how are authorities containing it?
What is the Nipah virus?
The highly pathogenic zoonotic virus Nipah (NiV) causes death in 40 to 75% of human infection cases due to its high rate of human transmission. One of the most well-known viruses in the paramyxovirus family, NiV, is one of the most well-known viruses from the henipavirus genus, which causes a variety of neurological – frequently respiratory – diseases in both people and animals, in addition to the Hendra virus, which can be found in Australia.
Fruit bats of the Pteropodidae family, ubiquitous across Oceania, South and Southeast Asia, and sub-Saharan Africa, are natural reservoirs of the virus, meaning the virus naturally lives and reproduces in these mammals without causing them any harm.
The virus can either directly or indirectly spread to humans via intermediary hosts like pigs or horses that encounter them.
What signs indicate the Nipah virus?
The human NiV infections range from asymptomatic infections to severe seizures, brain inflammation, and encephalitis (inflammation of the brain) according to the World Health Organization (WHO).
The clinical presentation of NiV infection is neurological, affecting the central nervous system and resulting in acute encephalitis syndrome (AES), characterised by seizures, confusion and loss of consciousness. Acute respiratory distress syndrome (ARDS) can develop as a result of the disease’s progression and can harm the lungs.
The virus’s estimated incubation period ranges from four to fourteen days.
Where have there been Nipah virus outbreaks before?
In 1998, pig farmers and butchers from Malaysia and Singapore contracted the virus from infected pigs. More than 100 people died as a result of the outbreak, which affected more than 250 people.
There have been subsequent, almost annual outbreaks in Bangladesh since 2001, with human infection traced to the consumption of date palm sap contaminated with urine or saliva from infected fruit bats.
Equine slaughter and consumption of infected horse meat were associated with NiV infections in the Philippines in 2014, according to reports.
West Bengal was the site of two outbreaks in 2001 and 2007 according to India. In 2018, South India reported its first NiV outbreak in Kerala, when 19 confirmed cases led to 17 deaths. Since then, almost every year, NiV spillovers have been reported in Kerala.
What has happened in Kerala?
Only two of the 10 incidents involving NiV spillover in Kerala ended up being outbreaks with human-to-human spread, despite Kerala’s 10 since 2018.
Instead of a cluster or outbreak like in 2018, Thekkumkara Surendran Anish, nodal officer at the Kerala One Health Center for Nipah Research and Resilience, stated, “We are now reporting single cases of Nipah infections.”
The last six NiV infections in the state have been single-case spillovers with no human-to-human transmission. Anish believes that the state’s strengthened surveillance system is to blame for the recent rise in recorded cases.
We don’t know the cause, but thousands of people die annually in India as a result of AES or ARDS, respectively. NiV, in fact, is not a common cause for respiratory and encephalitis syndromes”, he said. However, in Kerala, more Nipah infections are being discovered because the entire health system places a premium on it.
It’s also concerning that all four NiV infections were identified in a limited number of days and in a limited area, Anish continued. “Four independent spillover events within a couple of months in a 50km radius suggest a very high presence of infected bats and the virus in the area.
What it says is that there are “high chances” of Nipah spillovers in some geospatial areas of Kerala, primarily because the bats there appear to be very contagious for a short while of the year.
What is causing Kerala to become a hub for the Nipah virus?
Unlike in Bangladesh, where there was a dedicated channel for the virus to spill over to humans (contaminated date palm sap), there is no obvious source in Kerala – or, at least, the” spillover mechanism “so far remains unclear.
The exact spillover mechanism is unknown, but Kerala’s “high sporadic” phenomenon strikes us as highly sporadic. You might come into contact with an infected bat or its droppings without knowing, for instance, Anish said.
The commonly accepted cause is spillover from the human consumption of fruits contaminated by bat saliva or urine. However, so far, virological analysis of bat-baked fruits has turned inconvenient.
The Indian Council of Medical Research’s most recent study suggests that the virus may be spread by air.
” Disease-causing microbes have different routes of transmission to reach and infect human hosts, “Thekkekara Jacob John, one of the authors of the paper, and an emeritus professor at the Christian Medical College, Vellore, said”. One of them is “airborne transmission,” similar to how it is with tuberculosis, where microbes stay a long distance in the air and are inhaled far away from the source.
The authors of the paper support their hypothesis, which allows for the rare but frequent spillovers of NiV in Kerala, where mechanical vectors like those found in Malaysia and Bangladesh are lacking.
What steps are Kerala’s authorities taking to control the Nipah virus?
Kerala has been successful in using trace-and-test techniques to stop the virus from spreading. Across 10″ spillover events”, the case count stands at just 37 infected individuals.
An effective surveillance system is essential, according to Anish. All primary contacts of a patient who has a Nipah case are immediately tracked and monitored through house quarantine. If they test positive for the virus, we immediately start antiviral treatment, “he said.
The use of broad-spectrum antiviral drugs as a preventative measure of “primary contacts” has reduced mortality. According to our knowledge, if we can treat Nipah early, it will undoubtedly be treated, “Anish said.
” Syndromic surveillance is another crucial aspect, whereby, in hospitals across the state, any patient presenting with AES or ARDS is tested for Nipah, “Anish said.
Kerala’s health system has been steadily improving. Four laboratories in the state now have the ability to perform reverse transcriptional polymerase chain reaction (RT-PCR) tests for the identification of active NiV infections.
” It all comes down to political commitment, “Anish said”. The state makes sure that all efforts to combat Nipah outbreaks are kept under control by the entire healthcare system.
How is the Nipah virus treated? Is there a vaccine in development?
For its Research and Development Blueprint, a global strategy and preparedness plan for epidemics, the WHO has named Nipah as a priority disease.
The University of Oxford’s NiV vaccine, which started in-human trials in January, received funding from the European Medicines Agency (EMA)’s Priority Medicines (PRIME) program in June.
However, there are no drugs yet available that specifically target NiV infection.
Doctors have used broad-spectrum antivirals because there are no approved treatment protocols for NiV and because of the high mortality risk. The antiviral of choice is ribavirin, which has been proven to work well in several cases against NiV infections in people.
During a 2023 outbreak in Kerala, early application of the antiviral Remdesivir resulted in an improved case fatality rate. In addition, monoclonal antibodies (copying of antibodies created in a laboratory) have been used to stop severe illness from manifesting in high-risk people.
How can zoonotic viruses like the Nipah virus be avoided?
According to Anish, NiV is a model case study for a” one health “approach to combating high-threat pathogens. The one health approach acknowledges the link between the health of people, animals, and the environment.
Anish said that “one health” is a combination of three things: human health, animal health, and environment health. You have to tackle all these things to reduce the chances of zoonotic spillovers such as Nipah. “
Zoonoses, which are transmitted from animals to people, account for approximately 60% of new human pathogens. These zoonotic viruses primarily developed as a result of ecological disruption and the spread of human populations into wildlife habitats.
Source: Aljazeera
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