Swine flu still poses a deadly threat
While H1N1 mostly causes mild disease, some people — estimates suggest fewer than 1 percent — become deathly ill, very fast; experts warned that these cases could overwhelm hospitals
Swine flu has still not grown more severe, as many feared it would but as the pandemic’s second, autumn wave begins in the northern hemisphere, the virus is posing a different threat. While H1N1 mostly causes mild disease, some people — estimates suggest fewer than 1 percent — become deathly ill, very fast.
Debora MacKenzie writes that at a meeting last week in Winnipeg, Canada, experts warned that these cases could overwhelm hospitals. “These were the sickest people I’ve ever seen,” says Anand Kumar, an intensive care expert at the University of Manitoba in Winnipeg.
Kumar helped manage a wave of severe cases in the city in June, mostly in young Canadian aboriginals, who required the most advanced care. “This pandemic is like two diseases,” he says. “Either you’re off work a few days, or you go to hospital, often to the intensive care unit. There’s no middle ground.”
In the southern hemisphere, 15 to 33 percent of hospitalized cases went to ICU in the past two months. “That’s very high for flu,” says Richard Wenzel of Virginia Commonwealth University in Richmond. “When this flu is bad, it’s very bad.”
Lung attack
In these cases the virus rapidly destroys the lungs’ alveoli, where gas transfer occurs, often causing acute respiratory distress syndrome (ARDS), which usually kills in half of all cases. Antoine Flahault of the School of Public Health in Rennes, France, found that this past winter in Mauritius and New Caledonia, HiN1 caused ARDS 100 times as often as ordinary flu.
The direct viral damage inflicted on the lungs by severe H1N1 contrasts with SARS and bird flu, the impact of which is mainly due to a runaway, body-wide immune response, says Kwok Yung Yuen of the University of Hong Kong, China. This means early suppression of H1N1 with antivirals is crucial, which in turn requires spotting cases fast.
Who will get severe H1N1? Kumar is coordinating a multi-hospital study of severe H1N1 to find out, but says preliminary results suggest severity is linked to HLA, a genetic variation in immune systems. This could be why flu is worse in some ethnic groups.
McKenzie writes that what haunts ICU doctors now is whether they will have enough beds for the coming second wave. If not, they will have to decide who to prioritize. ICU space is already tight, and studies in the United Kingdom and the United States have found it may not be enough. Australia managed to increase ICU capacity just enough to cope during its flu season, which is ending, says Kumar. “If we don’t prepare, it could be really bad,” he warns.
