There is an increase in swine flu (HINI) cases observed in the capital Delhi and several other states in the country. Karnataka state has registered over 4,000 cases, while Delhi reports more than 1,700. Given the continuous rise in infected individuals, concerns have arisen regarding the emergence of a new swine flu strain.
However, the Institute of Central Medical Research (ICMR) clarified that no new H1N1 (swine flu) strain has been detected in India; the infection is caused by the old strain. This raises the question of why the number of cases is increasing if there is no new strain, and when a decline in morbidity can be expected.
One factor contributing to the rise in cases is changing weather conditions, but another significant reason lies within the body's immune system. To understand this, one must look back at the events of 2009. In May 2009, the first case of swine flu was recorded in the country. Subsequently, during the winter period (from December 2009 to March 2010), the number of cases rose again, leading to widespread infection among the population. After this, cases gradually began to decrease. Later, between 2014 and 2015, there was an outbreak of swine flu affecting thousands of people, and in 2019, a sharp jump in morbidity was observed. Currently, in 2026, elevated figures are being recorded.
Professor Dr. Jugal Kishor, Director of Community Medicine at Safdarjung Hospital, explained this phenomenon. He noted that in India, swine flu cases increase at certain intervals. This pattern indicates that the H1N1 virus never completely disappeared but remained among the population, periodically causing outbreaks.
According to Dr. Kishor, when a large number of people become infected with any virus, immunity against it is formed, which lasts for many years. Because of this, subsequent outbreaks are not massive but only consist of minor episodes. However, over time, the level of immunity in the body gradually decreases, leading to a renewed rise in cases. This happens cyclically every few years.
He provided an analogy: if many people in a certain area were previously infected with swine flu, they developed immunity, and the infection remained low for several years. But as time passed, the body's ability to fight this virus weakened, which once again caused an increase in morbidity. Dr. Kishor emphasized that no virus disappears forever; when immunity weakens, the virus begins to infect people, causing a rise in cases.
During rains and changes in weather, flu cases may increase. Conditions such as heat, rain, and high humidity promote the spread of the virus. Furthermore, people often come into close contact with each other in offices, schools, metros, and other enclosed spaces. If someone has the flu, small particles released during coughing or sneezing can be transmitted to other people.
Dr. Kishor believes that as long as a sufficient level of herd immunity has not been established in society, cases will continue. This means that when a large portion of the population becomes infected and develops immunity to swine flu, the number of cases will naturally begin to decrease. Such a cycle of declining morbidity is characteristic of viral infections, and there is no need for panic. Most people experience only mild symptoms.
Swine flu will not lead to an epidemic. The public is advised to consult a doctor and get vaccinated against the flu for prevention.
