H5N1 Bird Flu replicates more strongly than common flu-study
Pastor Dale Morgan
*H5N1 Bird Flu replicates more strongly than common flu-study*
10 Sep 2006 16:59:56 GMT
Source: Reuters
HONG KONG, Sept 11 (Reuters) - The H5N1 bird flu virus replicates far
more aggressively in people than common human flu viruses, a study of
patients in Vietnam has found, offering further insight as to why the
virus is so deadly.
The study, in the latest issue of Nature Medicine, also found that the
virus had got into the blood stream of many of the human victims it
killed, which means the virus could have spread to other parts of the body.
Menno de Jong, a key researcher in the study, explained that the
unusually high viral loads triggered intense "cytokine" responses -- an
immune system overreaction that can be fatal.
Cytokines are proteins in the immune system that fight off intruders
such as bacteria and viruses.
"During H5N1 infection, the (cytokine) response seems to be very, very
intense. Cytokines want to get rid of this intruder but if you have very
high levels of cytokines, it can also damage the body ... it can be
directed against your own cells and organs," de Jong told Reuters in an
interview.
The study involved 18 people infected with H5N1 and 8 with human flu in
2004 and 2005 in Vietnam.
Scientists found far higher viral loads in the nose and throats of those
infected with bird flu than human flu.
Thirteen of those infected with H5N1 died and the virus was found in the
blood of at least 9 of them, implying it could have been transported out
of the respiratory tract.
The virus was also found in the rectums of most of those with H5N1,
suggesting it could have spread through the blood stream into the
gastrointestinal tract.
Those with common flu had no virus in their blood or rectum. No one died
in that group.
"The fatal outcome of H5N1 infections seems to be associated with high
levels of replication of the virus and also the detection of the virus
in the blood," said de Jong, of the Oxford University Clinical Research
Unit at the Hospital for Tropical Diseases in Ho Chi Minh City in
southern Vietnam.
The team was able to draw a connection between those who were most ill
and the level of cytokines found in them.
"We found that levels of cytokines were much higher in H5N1 patients
than in the human flu cases. Again, the highest levels of cytokines were
found in those who died of H5N1," he said.
"The high levels of the virus triggered an overwhelming inflammatory
response that contributed to lung dysfunction and eventual death."
De Jong highlighted the need to stop the virus replicating.
"What's important is to stop the replication as soon as possible, so you
prevent damage to the lungs and prevent the inflammatory response to the
virus," he said.
But he conceded that early diagnosis was a challenge, especially in
remote places where health services were not readily available.