Of Pigs and Men

When I started working at CDC as an EIS Officer in the Influenza program, there was a lot of focus on pigs as the source of novel influenza viruses. It was called the mixing vessel theory and in retrospect it was my introduction to the importance of infectious disease ecology to prevent microbial threats. Pigs can be infected by multiple different influenza viruses and “mix-up” their 8 genetic pieces to create a brand new or reassortant virus. The new H1N1 flu virus appearing in different parts of the world has genetic pieces from human influenza, bird influenza, and 2 different types of pig influenzas. It has been referred to as a quadruple reassortant.

There have been some interesting speculations on the origin of the virus. Early information suggests that this new influenza strain took off in Mexico towards the beginning or middle of March and spread within the country before being picked up by a routine influenza study in California. However, the genetic make-up of this virus implies US and Eurasian swine virus ancestors and suggests that this new virus will end up having a very interesting origin and pedigree. Mexican Health officials have confirmed the first patient as a small boy in a village in the eastern state of Veracruz who became ill at the end of March. The Food and Animal Organization [FAO] and the World Animal Health Organization [OIE] have sent teams to assist in the investigations and CDC has been offered an opportunity to join and provide our expertise.

There is a lot to be learned about this new disease including how well it is transmitted and how severe of a disease it can cause: in the United States disease severity seems to be similar to seasonal flu. This new information will determine how we prevent future spread of the disease. The current news reports are of over 1890 infections and 23 countries have officially reported cases of influenza A (H1N1). Approximately 2000 laboratory confirmed and probable cases with 2 deaths have occurred in 43 US states. Mexico has reported over 1200 confirmed infections and 44 deaths. In our response to this new outbreak, it is important to remember that seasonal influenza viruses are currently pandemic and kill 36,000 each year.

While we wait for more public health information, please take this opportunity to update your personal preparedness plan. Some good sources are:

• PandemicFlu.gov – Preparedness Checklist [PDF, 1 page]
• Fema.gov – Are You Ready