The Return of Swine Flu: Mexico vs. U.S.

Those who boldly predict the outcome of influenza do so at their own peril.

The 2009 Swine Flu outbreak in the U.S. and Mexico is different than previous outbreaks. The key issue today is why deaths have been reported in Mexico and not elsewhere. The same virus is attacking the same age group - healthy young adults - in the affected countries. So, the difference in outcome must be differences among the patients. This is likely due to one of three things: in Mexico, the patients have more secondary bacterial pneumonia (e.g. with Staph or Pneumococcus), or co-infected with flu virus and another virus, or there is more damage to the lungs given the high level of pollution in Mexico City.

Since the cases in the U.S. are mild, it cannot be the rapid access to ICUs here that is saving lives - as some have speculated. Furthermore, the antivirals are weak therapeutic agents, which disproves that our access to therapy is saving patients with the disease.

The good news is that we have two antivirals that are effective against the circulating strain of Swine Flu. The key point, however, is that each offers excellent protection as a prophylactic agent- from recent studies of the antivirals about 70% of exposed but not ill people can be spared infection. Yet both drugs are marginal as therapeutic agents, and neither has been rigorously tested in life-threatening cases of flu. That is the reason to seek a safe and effective vaccine.

There are important lessons from prior influenza and Severe Acute Respiratory Syndrome (SARS) pandemics:

* Accurate and early reporting of all cases globally is essential for control. The delays in reporting the initial cases of SARS in China contributed to its early dissemination.

* Infection Control in hospitals must be assiduous to avoid spread to health care workers and other patients. This was noted early in Canada with the SARS pandemic, and rapid interventions led to its control there. Specifically, handwashing and prudent use of masks are helpful and effective. If the new Swine Flu strain shows occasional ability to be airborne within microscopic droplets, the use of negative air pressure rooms - if available to keep the air currents going only in the direction of the patient's room- may help.

* Lastly, the need for psychological support of health care workers was not fully appreciated early in the SARS outbreaks. These dedicated men and women are overepresented by young adults- susceptible to Swine Flu. Careful attention to their needs and support for their families would be essential.

In 1976, when my colleagues and I reported two patients in Virginia with Swine Flu, it added some concern that the original cluster at Fort Dix had spread beyond New Jersey. President Ford received impassioned advice from health policy experts at that time and strongly advocated a national vaccine program. Subsequently, there were two unexpected outcomes: The Swine Flu epidemic never materialized, and the vaccine unexpectedly caused a 7-fold increase in a neurological side effect leading to weakness and paralysis, the Guillian Barre Syndrome. A shakeup at CDC followed, and for years the public's willingness to accept vaccines was diminished.

It is unclear if Swine flu will act more like the devastating avian flu pandemic of 1918-19 or the fizzled Swine flu outbreak of 1976. However, the latest "influence" to visit itself upon the citizens of the world reminds us that epidemics are part of the natural interaction of people and microbes throughout civilization. Yet each time we react as though we have discovered something new. The only really new things are our surprise and consistent inability to recall all of the lessons from prior visitations.