COVID-19 and the fear around it may have gone away, but over the past few weeks, India has been rocked by cases of fever and intense coughs. People across States have been falling sick, and some have even had to be hospitalised. Last week, the Indian Council of Medical Research said these cases are linked to Influenza A, the H3N2 subtype virus that causes flu. The Council said surveillance data had shown a spike in these cases in India. So what is the H3N2 virus? Who is vulnerable to it and what symptoms can it cause? Is there a vaccine that can be taken?