Nipah Virus Incidence in Kerala
The recent Nipah virus case reported in Kerala involves a 42-year-old woman testing positive on May 8. This marks the third occurrence in Malappuram district over the last two years. Previously, a 14-year-old boy and a 24-year-old adult tested positive in 2022.
Previous Outbreaks and Spillovers
- Outbreaks: Kerala experienced outbreaks in 2018 and 2023 with human-to-human transmission.
- Spillovers: There were four spillover events in 2019 and 2021, and two in 2024.
Characteristics of Spillovers and Outbreaks
- Spillover Characteristics:
- Generally restricted to a single case with no human-to-human transmission.
- Patients present with acute encephalitis syndrome (AES).
- Outbreak Characteristics:
- Index cases present with acute respiratory distress syndrome (ARDS).
- ARDS patients have high viral loads and severe lung involvement, facilitating human spread.
- High severity of ARDS leads to greater mortality.
Clinical Findings
- Throat swab samples are a key indicator for human spread, especially in ARDS cases.
- In 2018, there were 17 deaths out of 18 cases; in 2023, there were two deaths out of six cases.
Genetic Studies
- An ICMR-NIV Pune study revealed small genetic variations in the 2018 virus from the Bangladesh strain.
- Emphasis on conducting quick genetic studies of the virus in humans and bats.
- Importance of sharing genetic sequences in public databases for better study and understanding.
Conclusion
Given the frequent occurrences of Nipah cases in Kerala, the need for routine studies of natural hosts, such as fruit bats, is crucial. Detailed genetic studies are vital to understand the virus's evolution and prevent further outbreaks.