Tosh said that even in a healthy child, the body can overcompensate, sending white blood cells flooding into the lungs. This can overwhelm the body and cause serious consequences.
“If the body’s reaction to the virus is too vigorous, this can cause as much damage as the virus itself,” he said.
Flu strains are named for molecule types surrounding the outside of the virus particle. There are 17 different types of hemagglutinin, or H particles, which allow the virus to bind to cells. There are nine different types of neuraminidase, or N particles, that allow the virus to spread the infection throughout the body.
H3 subtypes tend to lead to the largest number of hospitalizations and deaths, particularly for children, the elderly and anyone with a compromised immune system, Tosh said. To complicate matters, this year’s strain is not well-matched to what was predicted by the surveillance community, so the current vaccine is not a great match, he added.
“Some would speculate that this means the vaccine won’t work as well, but that has not been proven,” Tosh said. “You should still get your flu shot because it’s the best protection we have.”