The Two Faces of Swine Flu

The sun is making more frequent cameos in our part of the world, suggesting summer may be on its way. Another, but less obvious, indicator of the change in seasons is the gradual decline in patients with swine flu (H1N1 09 influenza) needing treatment in our intensive care units.

The last  ‘Life in the Fast Lane’ comment on swine flu was made before the pandemic was declared, and centered on what exactly the pandemic would mean. Due to the luck of the seasons those of us in the Southern hemisphere got the first chance to find out. Now we are in the process of handing the baton onto our friends in the North, as their winter approaches.

WHO FAQ: What is phase 6?

The swine flu pandemic has shown two faces. Initially, from the emergency department perspective, the ‘whole swine flu thing’ was a nuisance. Hordes of the ‘worried well’ attended emergency departments with their coughs and sniffles. Swabs were thrust up countless noses and into countless throats so that the big brains in the ivory towers could track the approach of the predicted tsunami. Some patients, at least, were rewarded with some tamiflu tablets to take before they were sent on their way.

Complacency was unavoidable. There seemed to be a lot of ‘hoo-hah’ about an illness that was much like the usual seasonal flu, perhaps not even as bad. Then, as the wave crashed, the spotlight fell on the other face of the swine flu pandemic. It is true that the attack rates of swine flu, and the resulting mortality, has been lower than expected. Yet, intensivists in Australia and New Zealand have seen patients requiring long stays in ICU and high rates of bed occupancy – at peak times patients with swine flu occupied 1 in 4 ICU beds (higher in some centers). Instead of the predicted 10%, the percentage of hospitalised patients needing ICU admission was more like 20-25%. This discrepancy – decreased mortality coupled to higher-than-expected impact on critical care services – has been called the swine flu paradox.

During a pandemic the cases offer but slight difficulty. The profoundness of the prostration, out of all proportion to the intensity of the disease, is one of the most characteristic features.

William Osler on Influenza In: The Principles and Practice of Medicine 1909: 155

The patients themselves were different. The expected patients with comorbidities (e.g. the immunosuppressed) were prevalent, but many patients were  young – sometimes with no other medical problems – or simply obese or smokers. Tragically, the virus found a hunting ground among the pregnant. With disproportionate numbers of young people fighting for their lives on ventilators for weeks or even months,  the swine flu has been nothing like the seasonal flu we’re used to. The relative youth of those who die means that the number of life-years lost during the pandemic may be paradoxically high.

On rare occasions this new enemy has shown itself to be a devious foe, with an ability to mutate and develop resistance to antivirals.

WHO encourages clinicians to be alert to two situations that carry a high risk for the emergence of viruses resistant to oseltamivir.

1. The risk of resistance is considered higher in patients with severely compromised or suppressed immune systems who have prolonged illness, have received oseltamivir treatment (especially for an extended duration), but still have evidence of persistent viral replication.
2. The risk of resistance is also considered higher in people who receive oseltamivir for so-called “post-exposure prophylaxis” following exposure to another person with influenza, and who then develop illness despite taking oseltamivir.

Increasingly, cutting edge therapies like new antivirals and extra-corporeal membrane oxygenation (EMCO, a type of cardiac bypass) are being used to combat the three main ways that swine flu tries to kill people:

• viral pneumonitis with bilateral lung infiltrates, also called “flu-A”-associated acute respiratory distress syndrome or ‘FLAAARDS’. Sometimes associated with multi-organ dysfunction syndrome (MODS).
• secondary bacterial infection.
• viral exacerbation of pre-existing lung disease.

Fortunately there have been many success stories, but there have also been tragedies. Many lessons will no doubt be learnt from this, the first pandemic of the 21st century. The ANZICS Influenza Registry, which has collated information from every swine flu patient admitted to an ICU since the beginning of June 2009, promises to be an invaluable resource for the future.

Finally, as the swine flu vaccine rolls out, its hard not to peek ahead to next year. The WHO have already advised that coverage of this year’s swine flu strain should be included in the 2010 seasonal influenza vaccine for the southern hemisphere. Uptake of the vaccine, among the relatively young in particular, may determine the future impact of swine flu from a critical care perspective.

I would like to issue a Mount Carmel-like challenge to any ten unvaccinated priests of Baal. I will take ten selected vaccinated persons, and help in the next severe epidemic, with ten unvaccinated persons (if available!). I should choose three Members of Parliament, three anti-vaccination doctors, if they could be found, and four anti-vaccination propagandists. And I will make this promise – neither to jeer or to jibe when they catch the disease, but to look after them as brothers; and for the three or four who are certain to die I will try to arrange funerals with all the pomp and ceremony of an anti-vaccination demonstration.

William Osler, from Man’s Redemption of Man 1910: 44-45

Links and references

• 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
• 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.
• Antiviral use and the risk of drug resistance (WHO)
• Pandemic influenza vaccines: current status (WHO)
• WHO recommends vaccine composition for 2010 influenza season in southern hemisphere (WHO)
• Flu Pandemic Pushing Demand for ECMO (Elsevier Global Medical News)

Life in the Fast Lane ‘swine flu’ posts

• Lessons from 1918
• Swine Flu in ICU
• What do you mean pandemic?
• H1 N1 DON’T PANIC!
• The Two Faces of Swine Flu