One of the world's worst fears is unfolding as we watch the emergence and spread around the globe of a strain of H1N1 influenza A swine influenza virus from Mexico. The virus, which contains the mixed genes from pigs, birds and humans, and appears to be highly transmissible among humans, has placed the world on high alert for an influenza pandemic.

In the past week it has spread widely from Mexico with confirmed cases in the United States, Canada, Austria, the United Kingdom, Germany, Spain, Israel and New Zealand. To date, nearly all of the deaths associated with infection with this virus have occurred in Mexico.

The U.S. Centers for Disease Control and Prevention has declared a public health emergency and the World Health Organization in Geneva has elevated the risk of pandemic transmission to Phase 5, the highest since WHO began monitoring the risk in 2003. Phase 5 is defined as widespread confirmed human-to-human transmission in two or more countries. Not since the last influenza pandemic in 1968, which killed an estimated 4 million people, has the world been at such high risk.

While there is clearly a need for heightened surveillance and preparedness, there are a number of uncertainties associated with this virus. First, although it is clearly a highly transmissible virus among humans, the genetic changes responsible for its increased infectivity are unknown.

Second, the virus appears to be a low pathogenic strain, but whether its high transmissibility will counteract the low virulence, as was the case in the Spanish influenza pandemic of 1918, is unknown at this time.

Third, it is uncertain what protective role, if any, the current vaccine will have against this virus, although most experts think it will not be protective.

Lastly, the normal influenza season in the northern hemisphere is past; it is uncertain what influence the warmer season will have on transmission and spread.

RAPID SPREAD

What is certain at this time is that the global human population is highly susceptible to this virus. The rapid spread of the virus in the past week makes it highly unlikely that it can be contained at this point in the epidemic cycle. Highly transmissible influenza viruses are primarily spread among population centers of the world by humans traveling via airplane. In 2008, it is estimated that more than 2 billion people boarded an airplane and flew somewhere, and nearly 700 million of these were in the U.S.

With such a massive movement of people via jet airplane, it is probable that this new influenza virus will continue to move quickly around the globe. Thus, although Hawai'i has not documented any cases of swine influenza to date, it is just a matter of time before the virus is introduced to the Islands. Prevention is the only option to decrease illness and death associated with pandemic transmission once the virus has been introduced to a community.

Effective epidemic prevention must be local. Although the federal and state governments have developed excellent preparedness plans (Hawai'i has one of the best in the nation), have stockpiles of antiviral drugs and vaccines, and are well prepared to do their part in preventing and containing transmission, the ultimate responsibility for decreasing the risk of exposure and preventing infection rests with individuals and the community where they live.

PREVENTION EFFORTS

There are a number of nonpharmaceutical prevention measures that are effective. On an individual basis, activities that place one close to large numbers of people should be curtailed, hands should be washed frequently with soap and water, mouth and nose should be covered when you cough or sneeze, stay home when you are sick, even if you think it is not influenza, and wear a mask when in crowds.

At the community level, public outreach and education materials should be developed and disseminated widely and repeatedly in the community to keep the people well-informed. Social distancing should be encouraged by discouraging community gatherings of all kinds; contingency plans can be made to take care of children if schools are closed and to help the needy if warranted by intensive community transmission. Finally, every family should have at least a one-week supply of food and water on hand.

This is an emergency that we have been preparing for over the past five years. It is important that the citizens of Hawai'i stay calm and informed, and follow instructions of local and state health agencies. The state and federal health agencies are well prepared to help local authorities deal with the emergency, but they are not prepared to reach all of the people. Only individuals and the community where they live can develop and implement effective prevention and control during pandemic influenza transmission.

Dr. Duane J. Gubler is director of the Emerging Infectious Diseases Program at Duke-NUS Graduate Medical School, and director of the Asia-Pacific Institute of Tropical Medicine and Infectious Diseases at the University of Hawai'i-Manoa's John A. Burns School of Medicine. He wrote this commentary for The Advertiser.