Swine Flu Saves Lives?

I read Richard Lehman’s roundup of the major medical journals nearly every week on doc2doc. He provides the perspective of a wise yet whimsical generalist who’s been ‘around a while’.

• Bishop JF, Murnane MP, & Owen R (2009). Australia’s winter with the 2009 pandemic influenza A (H1N1) virus. The New England Journal of Medicine, 361 (27), 2591-4 PMID: 19940287 (fulltext)

Lehman’s perspective on this was:

Tucked away in a commentary article about the Australian H1N1 influenza pandemic is the most startling observation:

A broader measure of all Australian deaths resulting from influenza or pneumonia currently indicates that there have been fewer such deaths than in other influenza or winter seasons.

Someone in the BMJ Rapid Responses had already seen these Antipodean figures some weeks ago and made the deduction that H1N1 saves lives. The pandemic strain seems to be displacing seasonal flu variants with higher overall lethality. We should be giving H1N1 a warm welcome, if only it didn’t kill young people preferentially.

The last sentence is the kicker really – it hints at the swine flu paradox – decreased mortality coupled to higher-than-expected impact on critical care services. Bishop et al summarize the Australian ICU experience thus:

A distinguishing feature of the epidemic was the number of people who were hospitalized in ICUs with confirmed cases of pandemic H1N1 influenza (3.5 per 100,000) and their young age (median, 42 years). According to data from influenza reports and from the Australian government, a total of 387 adults (over 20 years of age) were admitted with viral pneumonitis resulting from influenza A, as compared with a median of only 57 adults per year admitted with viral pneumonitis from any cause between 2005 and 2008. The peak of the epidemic in Australia lasted about 3 weeks, and although the Australian health system was stressed, there was spare capacity of ECMO equipment, hospital beds, and ICU beds.

It is because swine flu has ‘two faces’ that I do not welcome the 2009 H1N1 virus as a respite from its more lethal seasonal cousins. As it is the young that swine flu targets, even though fewer individuals may die, more life-years may be lost and at greater cost. That is why I had my swine flu vaccine, even though I don’t have the numbers to prove it.

Swine Flu Links and References

• ANZIC Influenza Investigators. Critical Care Services and 2009 H1N1 Influenza in Australia and New Zealand. N Engl J Med. 2009 Oct 8. (fulltext)
• Novel Swine-Origin Influenza A (H1N1) virus Investigation Team. Emergence of a novel swine-origin influenza A (H1N1) virus in humans. N Engl J Med 2009; 360:2605-15 (fulltext).
• Webb SAR, Seppelt IM, and the ANZIC Influenza Investigators. Pandemic (H1N1) 2009 influenza (“swine flu”) in Australia and New Zealand intensive care. Crit Care Resus 2009;11(3)170-2.

Life in the Fast Lane ’swine flu’ case-based Q&As:

• Pulmonary Puzzle #001
• Pulmonary Puzzle #006

Life in the Fast Lane ’swine flu’ posts:

• Swine flu – DON’T PANIC (includes updated links to swine flu resources)
• What do you mean pandemic?
• Lessons from 1918
• Two Faces of Swine Flu
• Swine Flu in ICU