A Vanderbilt researcher has a theory on why the H1N1 flu virus proved surprisingly deadly for an unusual group – that wasn’t seniors or infants. Among young and middle-aged adults at Vanderbilt intensive care, about one in five with swine flu died. WPLN’s Daniel Potter reports on a possible reason why.
In an article in the journal Nature Medicine, Vanderbilt’s Fernando Polack says a big factor in how individuals responded to the H1N1 pandemic flu was past encounters with regular seasonal flu.
He says adults may have gotten sicker with H1N1 because of their body’s own immune reaction, as their system tried to fight the virus the same way it would fight ordinary flu.
That’s by activating what’s called the body’s complement system, which normally boosts an immune response. But that didn’t work against H1N1 – instead the system went haywire.
“When the antibodies are not the right antibodies and cannot block infection, the complement may get out of control, as in this case, and end up hurting the host and in some cases even killing the host. And that is what happened to middle-aged people last year.”
Polack says an out-of-whack complement system makes vessels leak fluid, potentially in the lungs, making the patient sicker. And that proved particularly dangerous to people age 25 to 45.
Meanwhile Polack says babies weren’t affected as severely as some feared. That’s because infants lack antibodies from past seasonal flu encounters, so that didn’t complicate their response to swine flu. And he says many older people actually had the right antibodies for H1N1, from surviving a past pandemic flu in the 1950s.