This is a simple question, yet, surprisingly, we still don’t really know.
The primary organs damaged in H1N1 infections are the lungs. Damage may either be directly due to the virus or as a result of a secondary bacterial infection (viral and bacterial pneumonia, respectively). The role of direct action of the new H1N1 virus versus bacterial superinfections in severe cases is still unsettled. Early studies indicated few or no bacterial infections in patients with lab-confirmed infections. However, a more recent study (Louie et al. 2009) demonstrated bacterial infections of the lungs in 29% of the patients who had died of pandemic flu. Bacteria included Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, Streptococcus mitis and Haemophilus influenzae, in decreasing order of frequency.
So, bacteria appear to be present in some, but not all, fatal cases. One possibility is that people die for more than one reason. Some may die directly from viral infections while others die from bacterial superinfections. What are the implications of this possibility for treatment? Anecdotal reports suggest that Tamiflu decreases the severity of symptoms for most people diagnosed with pandemic H1N1. Antivirals may be regarded as an “upstream” treatment which decreases the damage done to the lungs by the virus. This might prevent both viral pneumonia, directly, and bacterial pneumonia, indirectly, by protecting the lungs from damage. If antivirals are not used, the lungs may fail as a result of direct viral damage. Some individuals may survive this initial assault but then suffer a second invasion by bacteria. If antibiotics are given in time, this may stop bacteria from doing irreparable damage to the lungs. If not, some patients may survive the virus only to die from bacterial infections. The final treatments for people with severely damaged lungs, mechanical ventilators and ECMO, offer some hope, but have relatively high failure rates.
The CDC is looking for patients with hemorrhagic pneumonia (see Coughing up blood for information). They suspect that it may be more common in patients infected with pandemic H1N1 than seasonal flu. Such patients may experience acute respiratory distress syndrome, which has a poor prognosis. As the CDC acknowledges, determining whether a person infected with H1N1 will go on to exhibit severe symptoms is difficult. Although some have underlying conditions, many do not. Some patients have gone from mild symptoms to death within 48 hours. If we apply the precautionary principle to H1N1 infections, the logical treatment is both antivirals and antibiotics.
We have the means to reduce death from pandemic flu – Tamiflu and antibiotics. Let’s use them.
Louie et al. (2009) Bacterial Coinfections in Lung Tissue Specimens from Fatal Cases of 2009 Pandemic Influenza A (H1N1) — United States, May–August 2009. MMWR Weekly. October 2, 2009. 58: 1071-1074.