The Union health ministry on Friday advised states to be on alert after two H3N2 deaths were reported from Haryana and Karnataka. There are four types of influenza viruses: A, B, C, and D. Influenza A and B viruses cause seasonal epidemics of disease in people almost every year in January to March and the post-monsoon season in India.
Influenza viruses are usually considered to be self-limiting and benign. “But this year, patients suffering from the infection are reporting prolonged cough, persistent fever and other complications. Hospitalisation has also gone up, necessitating increased vigilance,” said Dr G C Khilnani, chairman of PSRI Institute of Pulmonary, Critical Care and Sleep Medicine.
One of the reasons behind the increased virulence of the seasonal flu is the predominance of H3N2, a subtype of Influenza A virus, which causes more hospitalisations than the other subtypes, senior officials in the health ministry said.
According to the ministry, the ICMR network of laboratories has been monitoring human influenza virus in patients suffering from Severe Acute Respiratory Illness (SARI) and Influenza Like Illness (ILI) regularly. The trends observed from the beginning of this year, January 2 to March 5, clearly suggest pre-dominance of H3N2 which accounts for nearly 79% of all the influenza viruses found in samples taken from persons suffering from SARI or ILI. Influenza B Victoria (14%), a subtype of Influenza B, is the second most common virus subtype and Influenza A