H1N1 “Swine Flu” Virus Spreading—Not So Fast!

Photo courtesy of Centers for Disease Control

By Ed Martinez

July 9, 2009

More than 70 countries have reported cases of the H1N1 “swine flu” since it began to circle the globe last spring. The Centers for Disease Control and Prevention (CDC) said that a global pandemic is underway, and has raised the pandemic alert level to Phase 6.

The Phase 6 alert level is a reflection of the spread of the virus, and not necessarily the severity of illness caused by the virus. In the United States, most people who have been infected with the “swine flu” have recovered without requiring medical treatment. Most outbreaks have occurred in limited clusters, sometimes within a family or a school, but not spread much further. The CDC believes the virus could cause significant illness with associated hospitalizations and possible deaths during the flu season.

While it has been established that the virus is indeed spreading, this does not mean it is spreading from person to person as rapidly as other flu viruses. The CDC, and the Harvard-MIT Division of Health Sciences and Technology, have determined why the “swine flu” virus does not spread among humans as rapidly and effectively as other flu viruses. The H1N1 strain has a form of surface protein that binds ineffectively to receptors found in the human respiratory tract.

The researchers said that while the virus can bind to human receptors, it is clearly restricted. That restricted, or weak binding, along with a genetic variation of H1N1 polymerase enzyme, explains why the virus has not spread as efficiently as the seasonal flu. Harvard-MIT however, reminded us that flu viruses are known to mutate rapidly, so there is cause for concern if H1N1 undergoes mutations that improve its binding affinity. "We need to pay careful attention to the evolution of this virus,"  said Ram Sasisekharan, director of the Harvard-MIT Division of Health Sciences and Technology.

The CDC and U.S. government are clearly not taking any chances with the H1N1 virus, and have responded to the outbreak with the presumption that a pandemic was likely. “ We are working with our scientists to test and prepare a possible vaccine, and we are working with governments around the world to share what we know and learn from what is happening in their countries,” said the secretary of U.S. Homeland Security, Janet Napolitano. 

The CDC’s H1N1 immunization campaign will start in late September. Researchers warned that the strain might just need a single change or mutation to make it resistant to influenza drugs such as Tamiflu. Tamiflu works by helping to stop the flu virus from spreading inside the body. It can also help the virus from making you sick if you have been exposed to someone with the flu. Only time will tell how much of a threat the H1N1 virus really is to humans.