Decoding the deadly Nipah virus

Decoding the deadly Nipah virus

A virus named after Kampung Sungai Nipah, a village in Malaysia, where it was first discovered in 1998-99. The virus, that eventually killed 105 people in Malaysia, was first suspected to be Japanese encephalitis (JE) which, like the Nipah virus, induces brain inflammation. According to a paper by Dr K B Chua, who was a virologist in training at the University of Malaya when the disease broke out, “the outbreak of febrile encephalitis in humans was preceded by the occurrence of respiratory illness and encephalitis in pigs in the same region,” he writes, adding however, that at that point, the cause of swine mortality was assumed to be classical swine fever.

Suspecting, however, that it was not the mosquito-borne JE that was causing the spate of disease and death among the region’s pig farmers, he took samples of the virus to the Division of Arbovirus-borne Diseases, Centers for Disease Control and Prevention (CDC), Fort Collins, USA. “At CDC, Atlanta, the virus was rapidly identified as a novel paramyxovirus,” he writes.

The virus, which was traced back to the pigs, led to a large-scale culling of the animals in this region. Further studies indicated that the initial transmission from bats to pigs probably occurred, when pig feed was contaminated with bat excretions, says a 2007 paper, titled ‘Lessons from the Nipah virus outbreak in Malaysia’, published in The Malaysian Journal of Pathology.

Zoonosis

According to the World Health Organization (WHO), “A zoonosis is any disease transmitted from vertebrate animals to humans.” It could be caused by a virus, bacteria, fungi or parasite; some examples include anthrax, bird flu, ebola, dengue, rabies, malaria, swine flu and leptospirosis.

Bat eating fruit

Bat eating fruit

Nipah is believed to be transmitted from what are called flying foxes, or mega bats, so called because they are the largest bat species. They eat fruits and live in trees. These are a part of the old-world fruit bat family, called pteropid bats. Bats often end up being reservoirs for a number of severe infectious diseases, including Ebola, SARS coronavirus, Nipah and Hendra.

Transmission

In the case of Nipah, disease transmission or the means by which a pathogen can be passed from one organism to another, is believed to take place, “when one consumes infected fruits and fresh date palm sap contaminated by bats,” points out Dr Mahesh Kumar, Consultant – Internal Medicine, Narayana Health City. Which means, one should be careful while choosing their fruits. “Don’t eat those on the ground, especially if they have broken skin,” says Dr K Kolandaswamy, Director of Public Health, Tamil Nadu.

Loss of the natural habitat of the bat, appears to play some part in exacerbating the rate of bat-to-man transmission. The WHO says as much, says Dr Kumar. “As the flying fox habitat is destroyed by human activity, the bats get stressed and hungry, their immune system gets weaker, their virus load goes up and a lot of virus spills out in their urine and saliva,” he says.

Decoding the deadly Nipah virus

“Human-to-human transmission occurs due to direct contact,” says Dr N Devadasan, Director of Institute of Public Health, who led the WHO’s outbreak investigation team, when the infection broke out in Siliguri in 2001. That is perhaps why many healthcare providers who change sheets, clean bedpans and tend to the patient, end up being affected. Immediate isolation and ensuring that universal precautions are maintained in hospitals will help check the spread of the disease, agree all the doctors. “In India, if anyone falls sick, the entire family comes and visits,” says Devadasan. “It is better they keep away until the patient gets better.”

RNA virus

Nipah is an RNA or Ribonucleic Acid virus. “RNA viruses are the most common cause of emerging diseases in humans, attributable to the high mutation rate in RNA viruses compared to DNA viruses,” says the book Essential Human Virology. Nipah belongs to a genus (category, in layperson speak) called the Henipavirus; the Hendra virus, also found on pteropid bats, belongs to this category too. According to the CDC, “Transmission of HeV to humans has been invariably associated with close contact with ill horses, and transmission of NiV in Bangladesh is mainly through date palm sap contaminated with bat secretions.”

Biosafety Level 4

The virus, which is classified as Biosafety Level 4, meaning that it is highly infectious and needs a maximum containment facility, can be confirmed by an ELISA, RT-PCR or Serum Neutralization Test. The incubation period is anywhere between 5-14 days, but it can soon affect the respiratory and nervous system and patients can go into delirium or coma. Unfortunately, there is no definite treatment, except intensive supported care. “We need to maintain the vital functions,” says Kolandaswamy, adding that the earlier the condition is diagnosed, the better for the patient.

 

 

Source:- thehindu

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