Which H1N1 Flu Patients Need Antibiotics?

In the famous Spanish Flu H1N1 pandemic of 1918-1919 the enormous death toll was due, in 95% of cases, to a complication - bacterial pneumonia.   So it becomes an important question: how we can easily identify patients who are co-infected with bacteria who may need antibiotic treatment for pneumonia.  Some clinical features, such as the development of foul-smelling colored sputum, may suggest bacterial infection, but it’s not certain how reliable such features may be.  And not every patient can have a chest X-ray.

Australian physicians have just experienced a pandemic outbreak of H1N1, and involved physicians have reported relevant clinical findings in the Medical Journal of Australia.  Easily-measured clinical markers in patients infected with both the flu virus and a bacterium were compared with markers in patients with only the flu virus.

Patients with both the H1N1 virus and a bacterial infection were, in general, younger.  The most notable clinical differences between the two groups were the higher average respiratory rate and faster heart rate in those with influenza virus plus a bacterial pathogen.  Taken with other clinical features, this suggests that a respiratory rate of 25 or more breaths per minute and a heart rate of 100 or more beats a minute can help identify people who are more likely to need urgent clinical assessment and an X-ray.

We must realize that these are very simple criteria, that aren’t discriminatory if used alone.  But it’s useful to know that not everyone will need antibiotics, or even a chest X-ray.  However, the small proportion of patients whose flu is serious enough for them to be admitted to hospital will probably be treated with antibiotics as well as anti-viral medications (e.g. Tamiflu®).