NEW DELHI: Influenza cases have risen sharply in Delhi this season, with H1N1 accounting for the largest share of influenza A cases. However, the increase does not appear to be linked to a new or unusually dangerous strain, with the circulating virus showing changes broadly consistent with normal seasonal influenza.According to the information in the graphic, Delhi had recorded 2,612 H1N1 cases by Thursday, while the number of influenza A cases had crossed 3,300.Weather, crowding behind riseThe increase has been linked to a combination of humid, fluctuating and rainy weather, indoor crowding and poor ventilation. Increased person-to-person contact is also contributing to transmission, while H3N2 and other respiratory viruses continue to circulate.The Indian Council of Medical Research (ICMR) has said the circulating H1N1 virus is showing expected seasonal changes. The lineage has been circulating in India since 2025, and genetic changes observed so far remain consistent with seasonal influenza. There is no evidence of a new or unusually dangerous strain.There is also no specific evidence that international travel is driving the current rise. Local and seasonal factors such as weather, crowding and close contact appear to be more important.Symptoms can overlap with other infectionsCommon H1N1 symptoms include sudden fever, cough and sore throat, headache, body ache, fatigue and weakness. Children may also experience vomiting or diarrhoea.Doctors caution that these symptoms can overlap with H3N2 and other respiratory viruses, dengue, chikungunya and malaria. Symptoms alone, therefore, cannot confirm an H1N1 infection.Who needs greater caution?Older adults, young children and pregnant women are among those at higher risk. People with diabetes, asthma, COPD, chronic heart or lung disease, or weakened immunity also need to be particularly careful.H1N1 and Covid-19 are caused by different viruses. The Covid vaccine does not protect against H1N1, which has a separate influenza vaccine. Combined mRNA vaccines covering influenza and Covid are not commercially available.H1N1 is a subtype of influenza A, while H3N2 is another influenza A subtype. Influenza A and B can produce similar symptoms, with severity depending more on an individual’s risk factors and complications than on the H1N1 label alone.
Watch for warning signs
While most influenza infections can be managed with appropriate care, worsening symptoms warrant medical attention. Breathlessness, falling oxygen levels, chest tightness or discomfort, persistent or worsening cough or fever, confusion, dehydration, or symptoms worsening after an initial improvement are warning signs.
What people can do
People with influenza-like symptoms should stay home, wear a mask, cover coughs and sneezes and wash their hands regularly. Improving indoor ventilation and avoiding close contact while ill can help limit transmission.Adequate rest and hydration are also important. Annual influenza vaccination should be considered, particularly by people at higher risk.The message for Delhiites is one of caution rather than panic: the current rise is significant, but the available information does not point to a new or unusually dangerous H1N1 strain.
