Bacteria, Not Flu, Fatal in Past Pandemics

by Peter Collignon / Brisbane Times
May 29, 2009

IN THE past century we had three influenza pandemics. The worst was Spanish flu (1918-19), when tens of millions of people died.

The swine flu strain lacks one of the two essential characteristics needed to cause that kind of disaster. It readily spreads from person to person but it does not have a more aggressive (or virulent) effect in people compared to the winter flu strains.

The swine flu strain is not hyper-virulent. In the US, for every 1000 people who get infected, about 40 need to be admitted to hospital and one dies. Still aggressive, this virus is less so than many of the flu viruses that change slightly every year or so, and then circulate and cause epidemics (or pandemics) around the world, principally in winter.

This swine flu strain is an H1 strain. Variations of H1 strains have recirculated in people since 1918, and thus many may have some immunity already. This is reflected in the relatively low infection in people aged over 30. Even in children and young adults, with presumably little or no immunity, there does not seem to be excessive mortality compared to seasonal influenza. Again this reflects the relatively low virulence.

We need to consider what killed most people when new and virulent flu strains spread. It was bacteria, not the direct effect of the flu virus. Secondary bacterial infections, especially with pneumococcus and staph, caused nearly all deaths.

In 1918-19 there were no antibiotics. In the late 1950s when Asian flu struck, many deaths occurred because penicillin was the only antibiotic widely available and most strains of golden staph had developed resistance. Antibiotic resistance is a rapidly growing global problem.

Yet in Australia we still have a variety of antibiotics (especially injectables) that will work against nearly all strains of bacteria that might cause pneumonia.

Good hygiene can slow or stop the spread of flu virus. This means using alcohol hand rub and soap and water, masks and other general infection control measures, such as staying home if you are unwell.

We need to reconsider how we approach this virus. Flu strains every year cause proportionately more illness and deaths than this swine flu strain. Stricter controls will be necessary only when a new influenza arrives that is hyper-virulent and spreads easily.

Peter Collignon, an infectious diseases physician and microbiologist, is professor, school of clinical medicine, Australian National University.