Swine flu's edge: lesions in lungs

Swine flu's edge: lesions in lungs










July 14, 2009 - 11:17AM







The way swine flu multiplies in the respiratory system is more severe than ordinary winter flu, a new study in animals finds.
Tests
in monkeys, mice and ferrets show that swine flu thrives in greater
numbers throughout the respiratory system, including the lungs, and
causes lesions, instead of staying in the nose and throat as seasonal
flu does.
In addition, blood tests show many people
born before the 1918 flu pandemic seem to have immunity to swine flu
but not to the seasonal flu that hits every year.
The research by a top University of Wisconsin flu researcher was released on Monday and will be published in the journal Nature.
"I'm
very concerned because clearly the (swine flu) virus is different from
seasonal influenza," said study lead author Yoshishiro Kawaoka. "It's a
lot more severe."
But it is still not as severe as the 1918 influenza, he said.
With
only a few months since swine flu was identified, doctors are still
trying to get a handle on this flu strain and how it differs from the
yearly seasonal flu.
The latest study paints a more
pessimistic picture of the flu's strength and the vulnerability of the
elderly than how federal US health officials have been portraying the
situation.
Officials at the federal Centres for
Disease Control and Prevention said on Monday that swine flu is
behaving differently to seasonal flu and they are not comparing its
virulence to the run-of-the-mill influenza, which kills about 36,000
Americans a year. The CDC had no immediate comment on the Nature study.
Unlike
seasonal flu, the new swine flu is continuing into the northern summer,
and has caused severe illness mostly in younger people instead of the
elderly, the CDC said.
The CDC's Dr. Anne Schuchat
said late last month that people aged over 65, and maybe people over 50
"are less likely to get ill with this virus even when they're in a
family with somebody who has it."
A CDC study in May also found that one-third of older people had some immunity to swine flu.
Kawaoka
did not find that. He checked blood samples from a wide number of age
groups. With two exceptions, he found only people who were born before
the 1918 pandemic to have immunity.
W. Paul Glezen,
a flu epidemiologist at the Baylor College of Medicine in Houston,
Texas, who was not part of the study, said he would tend to agree with
the earlier CDC study on immunity, especially since the latest figures
show younger people became sicker.
Glezen also agreed with Kawaoka that the swine flu "appears to be more virulent than the seasonal" flu.
For
his study, Kawaoka tested three monkeys with swine flu and three with
seasonal flu. His data showed at least twice as much virus appeared in
all parts of the lungs, the tonsils, windpipe and nose for the swine
flu-infected monkeys.