New Delhi: The number of people falling ill in India due to H3N2, a subtype of influenza A virus, has doubled since the last spike in 2021, data from the Indian Council of Medical Research (ICMR) has shown.
With no clear reason in sight as to why people are becoming more susceptible to the virus — symptoms of which include fever, cough and fatigue — experts say that low popularity of flu vaccines, comorbidities and allergens in the air can be among the causes.
While the ICMR data is from just 27 of its laboratories, the Union government has been tracking the situation across all states real-time through its Integrated Disease Surveillance Project (IDSP).
Although doctors, health department officials and the government have been asking the public not to panic, the prolonged symptoms of the H3N2 virus has people worried.
Experts meanwhile are divided in their views on the H3N2 virus and the prolonged nature of its symptoms. A section of them feel that people’s immunity had lowered during the Covid pandemic since they had remained indoors for nearly three years, and sudden exposure to the outside world is making them susceptible to all kinds of viruses. Others believe that immunity will not be drastically affected that way.
According to the ICMR dashboard, the last spike in H3N2 cases, which took place between July to November in 2021, saw a maximum of 30 cases a week. The current outbreak has witnessed as many as 60 diagnosed cases a week. However, this is data from just 27 ICMR laboratories.
The government’s IDSP-IHIP (Integrated Health Information Platform), which casts a wider net with about 100 labs running across the country, has reported 3,038 confirmed cases of various subtypes of influenza, including H3N2, from the start of the year till 9 March. This includes 1,245 cases in January, 1,307 in February and 486 cases in March (till the 9th).
“We still need more data on the genome to understand if this strain is really responsible for severe and prolonged disease in patients. I must emphasise the need for people to get the updated flu shots every year,” Dr. Rohit Kumar Garg, a consultant with the Department of Infectious Diseases at Amrita Hospital, Faridabad, told ThePrint.
Also Read: 2 dead in India from H3N2 influenza virus, 90 cases so far in country
Is lower immunity a reason?
Explaining why patients may be seeing a longer spell of influenza symptoms, Gopi Chand Khilnani, a pulmonologist and chairman of the PSRI Institute of Pulmonary, Critical Care & Sleep Medicine, told ThePrint that every viral strain is different. “The disease course depends on three things — the agent, the host and the environment.”
The agent, in this case H3N2, is likely to have undergone changes in the genome. But the immunity of the host also plays an important part, Khilnani said. “Last three years, people restricted themselves indoors. Antibody levels wane over time. There was lower exposure in the last couple of years. However, along with this, the number of people who got their flu vaccines also reduced.”
“Once the pandemic got over, people went out with a vengeance,” Khilnani added, noting that this led to a sudden increase in exposure to viruses.
However, other experts say that lack of exposure does not affect one’s immunity.
“Our immune system has developed over millions of years to be able to fight off flu viruses. Three years of lowered exposure will not bring any drastic changes to our immunity,” said Jayaprakash Muliyil, epidemiologist and former chairperson of the Scientific Advisory Committee of the ICMR’s National Institute of Epidemiology.
“Just like the SARS-CoV-2 evolved to have new mutations, the flu virus too mutates. It is possible that there is a new variant of H3N2 circulating,” Muliyil told ThePrint.
“In any case, Indians were not very strict about masking even during Covid outbreaks. The infection was able to walk through the majority of the population. So this hypothesis has no basis,” he added.
It may be noted that influenza viruses that normally circulate in pigs are called “variant” viruses when they are found in people. Influenza A H3N2 variant viruses were first detected in people in July 2011. The virus itself was first identified in pigs in the US in 2010.
It’s not only H3N2 cases, but the number of people affected by influenza-like illnesses too are on the rise.
IDSP-IHIP data from health facilities indicate that in January this year, a total of 3,97,814 cases of Acute Respiratory Illness/Influenza Like Illness (ARI/ILI) were reported from the country that increased slightly to 4,36,523 during February. In the first 9 days of March, this number stands at 1,33,412 cases.
The corresponding data for admitted cases of severe acute respiratory illness (SARI) is 7,041 cases in January, 6,919 in February and 1,866 during the first 9 days of March.
People with comorbidities vulnerable
According to the health ministry, young children and old age persons with co-morbidities are the most vulnerable groups in the context of seasonal influenza. So far, Karnataka and Haryana have confirmed one death each from H3N2 influenza.
“India every year witnesses two peaks of seasonal influenza: one from Jan to March and other in the post monsoon season. The cases arising from seasonal influenza are expected to decline from March end,” the ministry said.
Doctors agree that severe symptoms are common in patients with other conditions.
Khilnani noted that while a majority of the patients were recovering within a few days of getting infected, those with predisposing conditions are the ones who are suffering from longer bouts of the disease.
He added that factors in the environment — such as pollutants and allergens (like pollen grains) are further exacerbating symptoms in patients.
Expressing a similar view, Garg, quoted earlier, said severity of the disease is more in people with predisposing conditions — such as heart disease, diabetes or chronic lung disorders. “Cancer patients who are on medications that suppress immunity are also at high risk, as are children below the age of 12.”
Garg noted that despite being updated every year to cater to the latest strain of influenza virus, flu vaccines are not very popular among Indians. “People who have chronic lung illness get their flu shots, but most people do not get them. This leaves them vulnerable to the constantly evolving strains of flu,” he said.
According to Dr Rahul Sharma, additional director, Pulmonology and Critical Care at Fortis Hospital Noida, though the acceptability for flu vaccine has marginally increased in recent years, especially in the post-Covid era, it is still suboptimal in the public. “People believe flu doesn’t harm them as much as COVID does,” he said.
While most healthy individuals have mild to moderate illness when infected, young adults with bronchial asthma or allergies that are not well controlled can have severe illness and complications, he explained.
Sharma also noted that people have become more vigilant about getting themselves checked when they have cold and cough symptoms for the fear of Covid — but they tend to limit themselves to just testing for Covid.
This is of concern with the ongoing surge in flu cases. There is a possibility that a person may have new or undiagnosed allergies that would put them at risk of severe disease from flu viruses, he explained.
The precautionary measures to prevent the spread of flu include wearing face masks, maintaining hand hygiene and social distancing, according to the health ministry.
However, Garg emphasises on the need to adopt the practice of staying up to date on the latest flu vaccinations.
(Edited by Geethalakshmi Ramanathan)
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