May 9, 2009

Life in the Time of Influenza

update written by Avram L. Nemetz, M.D. Medical Director

At the end of the week, it is useful to summarize and state clearly what has happened since we learned of the existence of the H1N1 virus on April 23.

We did not know this to be true three weeks ago, but a new influenza virus capable of efficient person-to-person spread has indeed emerged, and is disseminating rapidly through the human population.

To this point, lacking a key protein, the virus does not appear capable of causing the history-changing catastrophic death rates of the 1918 Spanish Flu, nor of the terrifying H5N1 Avian Flu, which still exists but has never developed the capability of sustained person-to-person spread.

An official pandemic will be declared by the WHO when clear evidence has been gathered showing illness spreading in communities outside North America. Health authorities are in no hurry to make an official pronouncement.

"We think perhaps two billion people will become infected, but of course we can't be sure how this will play out..." The realization will dawn only gradually on the public that we are living in a time of influenza. In a typical pandemic, about one third of the world's population is expected to experience clinical infection, about two billion people.

There is some public backtracking right now among World Health Organization officials, who are on the defensive over criticism of the WHO's handling of the pandemic's development, some of which reflects the public's misperception that a pandemic is automatically equivalent to a great disaster. The WHO (a U.N. organization) is being described in some circles as needlessly alarmist.

This is incorrect. A pandemic is a technical term for the worldwide spread of an infectious disease, in this case the newly sprouted influenza virus. The WHO has no flu severity categories yet-it was the U.S. CDC which developed their own pandemic severity category system only in 2007.

A flu pandemic can range in severity from a CDC Category 1 to Category 5. A Category 1 pandemic is less than a disaster, except for the three days you are sick with the flu. (A pandemic is mild when your neighbor has the flu. The same pandemic is moderately severe when you have it yourself.) A Category 5 pandemic would find us for a time trapped in a medieval plague, hauling out our dead for burial in mass graves. Even then, in the 10 pandemics over 300 years for which we have reasonably solid evidence, the case mortality rate has not appeared to be more than 2% worldwide, though 5% mortality or higher may have occurred in individual countries. India was extremely hard hit in 1918. One hundred million cases of influenza in the US with a 0.1% mortality rate still adds up to 100,000 excess deaths.

Those who are responsible for preparations should get accustomed to the idea that the pandemic is here now. Flu pandemics take fully two years to play themselves out. Though the early signs are reassuring that this could be a relatively mild event, the North American Flu Pandemic of 2009 will be fully visible only in retrospect.

_________________________________________

A decision on flu vaccine production is pending. It seems inconceivable that vaccine production for the new virus will not speedily be ramped up. But H1N1 vaccine production may interfere with our ability to produce and distribute seasonal flu vaccines. Tradeoffs and compromises are likely to be necessary.

The map of state-by-state spread shows laboratory-confirmed cases, but they represent thousands upon thousands of people who have had the flu but are uncounted. Most H1N1 influenza cases now are getting sick and recovering at home without medical attention.

The map which tracks flu spreading around the world is just getting started. It will be interesting to watch how different countries manage their own flu problems, because no country or region has the capability of avoiding its own outbreak when a pandemic occurs.

The mild flu virus presently spreading may be worse when a second wave rolls around the earth. Health officials already have had to debunk the idea of having "flu parties," in which parents deliberately expose their children to the current strain of flu, in the hope this will make them immune to a possibly more dangerous outbreak later on.

There is no evidence one way or another that this would be a good idea or a bad idea. Medically, there is a certain logic to it. Some people who do it would get unlucky, and have unnecessary complications. First, do no harm.