There are two flu viruses — Influenza A and B — that trigger seasonal outbreaks in individuals.

Currently circulating are the influenza A subtypes H1N1 and H3N2 and influenza B Yamagata and Victoria lineages.

H3N2, which has been the dominant strain circulating within the United States this 12 months, has been related to more severe flu seasons.

“So far during the 2022-23 flu season in the U.S., about 99% of those hospitalized due to influenza had H3N2 subtype,” says Jennifer Horney, PhD, an epidemiologist and founding director of the University of Delaware’s epidemiology program.

Research reveals that H3N2 typically causes extra extreme sickness in adults ages 65 and older.

The most typical signs of influenza A circumstances embody cough, congestion, sore throat, fever, headache, chills, physique ache, and fatigue.

Influenza A will be handled with supportive care along with antivirals like oseltamivir, baloxavir, peramivir, and zanamivir, says Adalja.

According to Horney, flu seasons pushed by H3N2 can embody extra circumstances of extreme ailments, hospitalization, and loss of life.

This is very true when vaccine protection is low or the vaccine just isn’t a great match to the circulating strains, she added.

“A lot of what determines the severity of the flu season has to do with the match of the vaccine to the circulating strain and the percentage of people who are vaccinated each year overall,” says Horney.

Influenza viruses are always evolving, and the flu vaccine have to be up to date yearly to stay efficient.

Occasionally, the flu virus mutates in a approach that reduces the effectiveness of the shot.

According to the Centers for Disease Control and Prevention (CDC), the flu shot is an effective match this 12 months — however protection within the U.S. is decrease than typical.

A study performed within the 2017-2018 flu season discovered that only one.5 % of 65,000 Indian adults ages 45 and older had ever obtained a flu shot, indicating that vaccine protection in India is probably going very low, says Horney.

In addition, air pollution — which is high in India — can worsen flu signs.

“Respiratory function is worse in a high pollution context,” says Adalja. “Any respiratory virus would be worse in those types of situations.”

As a consequence, the flu’s mortality rate is greater in India — notably amongst older adults and younger kids.

It’s “more than twice the rate per 100,000 people than in the U.S., where we expect between 30,000 and 70,000 deaths from influenza each year,” Horney mentioned.

India is monitoring an outbreak of influenza A (H3N2) that has led to 2 deaths. Though the uptick in circumstances is going on considerably later in India’s typical flu season, H3N2 circulates yearly. This 12 months’s shot is an effective match towards the circulating strains, and there are efficient antivirals that may deal with infections attributable to H3N2.