Swine flu has still not grown more severe, as many feared it would but as the pandemic鈥檚 second, autumn wave begins in the northern hemisphere, the virus is posing a different threat. While H1N1 mostly causes mild disease, some people 鈥� estimates suggest fewer than 1 per cent 鈥� become deathly ill, very fast.
At a , Canada, experts warned that these cases could overwhelm hospitals. 鈥淭hese were the sickest people I鈥檝e ever seen,鈥� 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. 鈥淭his pandemic is like two diseases,鈥� he says. 鈥淓ither you鈥檙e off work a few days, or you go to hospital, often to the intensive care unit. There鈥檚 no middle ground.鈥�
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In the southern hemisphere, 15 to 33 per cent of hospitalised cases went to ICU in the past two months. 鈥淭hat鈥檚 very high for flu,鈥� says of Virginia Commonwealth University in Richmond. 鈥淲hen this flu is bad, it鈥檚 very bad.鈥�
Lung attack
In these cases the virus rapidly destroys the lungs鈥� 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, .
The direct viral damage inflicted on the lungs by severe H1N1 contrasts with SARS and bird flu, whose impact 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.
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 prioritise. ICU space is already tight, and studies in the UK and US . Australia managed to increase ICU capacity just enough to cope during its flu season, which is ending, says Kumar. 鈥淚f we don鈥檛 prepare, it could be really bad,鈥� he warns.
