How deadly is it compared to the Coronavirus? | DW News

Key Concepts

• Nepa Virus (NiV): A zoonotic virus (transmitted from animals to humans) carried by fruit bats and pigs, causing fever and brain inflammation.
• Case Fatality Rate: The proportion of infected individuals who die from the infection (40-70% for NiV).
• Reproduction Number (R0): A measure of how contagious an infectious disease is; the average number of people one infected person will infect. (NiV R0 < 1, COVID-19 R0 2-3).
• Zoonotic Disease: An infectious disease that jumps from a non-human animal to a human.
• Epidemic Preparedness: Proactive measures taken to prepare for and mitigate potential epidemics and pandemics.
• Global SEPI Network: A coalition for epidemic preparedness innovations prioritizing development of NiV vaccines.

Nepal Virus Outbreak: A Detailed Overview

Initial Outbreak & Current Situation

Health officials in India have confirmed cases of the Nepal virus (NiV) in West Bengal state, prompting increased security measures, including screenings at airports across Southeast Asia, particularly in Thailand. Two confirmed cases were identified in December. Authorities are currently tracing nearly 200 contacts of the confirmed cases, with all tests conducted so far returning negative results, indicating no current widespread transmission. The World Health Organization (WHO) designates NiV as a priority disease due to its potential for rapid outbreaks.

Transmission & Severity

NiV is transmitted from animals – specifically fruit bats and pigs – to humans. Human-to-human transmission requires “very sustained long periods of close contact,” making it less easily spread than diseases like COVID-19. However, the virus is exceptionally dangerous due to its high case fatality rate, ranging from 40% to 70%. This means that a significant proportion of those infected will succumb to the disease. There is currently no approved vaccine or cure for NiV.

Comparison to COVID-19: Reproduction Number (R0)

A key difference between NiV and COVID-19 lies in their reproduction numbers (R0). COVID-19 had an R0 of 2-3, meaning one infected person would, on average, infect 2-3 others, leading to rapid global spread. In contrast, NiV’s R0 is currently below 1. This signifies that one infected person will, on average, infect less than one other person, causing the outbreak to naturally fade away relatively quickly. As Dr. Kaya Abbas stated, “if I’m infected by the time I recover I will actually transmit to less than one person. It will actually automatically fade away quite quickly.”

Historical Context & Global Distribution

The NiV was first identified over 25 years ago, in 1999. However, globally, there have been fewer than 750 confirmed cases. Outbreaks have been primarily limited to India and Bangladesh, with earlier, smaller outbreaks occurring in Singapore and Malaysia in 1999. Since 2001, the vast majority of cases have been concentrated in India and Bangladesh.

Vaccine Development & Future Risks

Despite the limited transmission currently, vaccine development is considered a high priority. Dr. Abbas explained that the Ebola outbreak highlighted the need for proactive vaccine development for pathogens with the potential to cause larger epidemics in the future. The Global SEPI network has prioritized NiV vaccine development, with several vaccine pipelines currently underway, though no vaccine is yet approved. The concern is that the virus could mutate and become more transmissible, potentially leading to a deadly epidemic. As Dr. Abbas noted, “currently the reproduction number is less than one but in the future it can potentially mutate and became more transmissible at which case it could be quite a deadly epidemic.”

Effectiveness of Current Measures

Current preventative measures, such as body temperature checks at airports, are considered largely sufficient given the limited transmission risk. Contact tracing within West Bengal has been thorough, with nearly 200 contacts of confirmed cases tested, all with negative results. Dr. Abbas emphasized that even within the affected region, spread is “extremely limited,” and the chance of international spread is “very very very unlikely.” He highlighted the success of contact tracing, stating, “the spread even within West Bengal very locally is actually extremely limited.”

Notable Quote:

“What makes it dangerous is the high case fatality rate like 40 to 70% of the people who get infected with Nepal virus will actually die from the infection.” – Dr. Kaya Abbas, Associate Professor of Infectious Disease Epidemiology and Dynamics.

Conclusion

The current outbreak of Nepal virus in India, while concerning due to its high fatality rate, is not considered to pose a significant global threat at this time. The virus’s limited transmissibility, as indicated by its R0 below 1, and the effective contact tracing efforts are mitigating the risk of widespread outbreaks. However, ongoing vaccine development is crucial to prepare for the possibility of future mutations that could increase the virus’s transmissibility and potentially lead to a more severe pandemic. Continued vigilance and proactive epidemic preparedness are essential.