A new strain of a relatively new viral species, called the Nipah virus, has caused a new outbreak in the Kerala State of India.
How It All Began
The outbreak started with three cases within the same family and a fourth case, who was a healthcare worker tending to the family. The mysterious infection had flu like symptoms, headache, vomiting and diarrhea. These symptoms elevated to much severe condition such as coma and So basically, nothing indicative of a specific kind of illness. All four infections resulted in death.
Blood samples of the initial victims confirmed the presence of Nipah Virus.
Bats and Pigs Spread the Virus
Its mechanism of transmission is just as strange as it symptoms. In, 1999, when the virus was first discovered, it was assumed that direct contact with infected pigs or their tissues led to infection. Later on, other causes were identified such as consuming fruits contaminated with bat saliva. The virus also transmits from human to humans, so healthcare providers are at special risk of infection.
Its Mortality Rate is Higher than Ebola
Surprisingly, Nipah virus has a higher mortality rate, even more than Ebola. Mortality rate simply means the risk of deaths in a population after infection. Nipah virus has a mortality rate of almost 75%, whereas Ebola has a mortality rate of 50%.
What Makes Nipah Virus so Deadly (and very strange)?
Each time there was a Nipah virus epidemic, a new strain was detected. A study published in 2016 by Mire et al., indicated that the strain responsible for the outbreak in Bangladesh (in 2001) was much more lethal than the previously identified strain from the Malaysian outbreak of 1999. The Malaysian strain was able to kill 50% of the infected monkeys, whereas all the monkeys died which were infected with the Bengali strain.
But how does a virus become more lethal in just two years? The answer lies in its genetic code which altered enough for it change its tissue tropism. This enabled the virus to leave the respiratory epithelium, and use the olfactory nerve as a passageway to enter the brain (a phenomenon described as change in tissue tropism). So yeah, it enters your brain through your nose, so strange [1].
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| Viral Particles found in Different Tissues of Infected Mammals. Source: Escaffre et al., 2013. |
Mire and co-workers also discovered that the the two strains were so different that antibodies against the Malaysian strain were ineffective against the Bengali strain.
Another strange behavior of the virus is that it attaches itself to the surface of white blood cells but doesn't infect them. When these virus carrying cells were injected into hamsters, they got infected and died [2].
Concluding Remarks
We still don't know what are the characteristics of the new strain in the Kerala epidemic. As of June, the death toll was 18 and the epidemic is now thought to have been contained. The mechanisms of pathogenesis are still elusive but the bigger picture shows that the virus changed its preference from infecting respiratory pathways to brain tissue.
References
1. https://www.ncbi.nlm.nih.gov/pubmed/23592639
2. https://www.ncbi.nlm.nih.gov/pubmed/27484128
3. http://www.who.int/news-room/fact-sheets/detail/nipah-virus
nice
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