In May, the 2007-08 influenza season officially came to a close. It will be remembered as the most severe in the past four years, causing the deaths of an estimated 69 American children. Meanwhile, the H5N1 virusthe avian fluwhich has been spreading among bird populations in Asia and other parts of the world, claimed its 241st human victim in April. While the two threats are separate, its critical that we view the influenza viruswhether seasonal or pandemicas a singular enemy.
We couldnt ask for a better dress rehearsal for a pandemic than the annual influenza season, when clinics and hospitals become real-life laboratories. The reverse is also truecontinued investment in pandemic planning has direct implications for seasonal influenza readiness. According to the federal governments National Strategy for Pandemic Influenza Implementation Plan One Year Summary, investment in pandemic preparedness could translate to a reduction in the number of deaths each year related to seasonal influenza. Improving disease detection and surveillance, utilizing anti-viral medications, and promoting healthy behaviors such as hand washing and cough etiquette could help reduce the spread of seasonal influenza.
So what lessons has the 2007-08 season taught us? Last month, I served as a co-chair of Seasonal and Pandemic Influenza 2008, an annual conference that brings together some of the most prominent global flu experts. Throughout the three days of the conference, the following issues rose to the top of the list of key lessons from the past flu season.
The public health community agrees: Vaccination remains the first line of defense. It is not, however, a panacea, as we are reminded when the vaccine is poorly matched to circulating strains. An analysis released in April by the Centers for Disease Control and Prevention estimated that this seasons vaccine was only 44% effective, which contributed to a severe season. But even a mismatched vaccine offers some degree of protection, and the CDC noted that it likely reduced the severity of illness in those who developed disease.
Despite years of effort, influenza vaccination rates remain lowat least 30 million doses went unused this year. It would be unfortunate if Americans, already lax about following the CDCs recommendations, used this years mismatch as an excuse for not being vaccinated next season.
The challenges with the vaccine served as a reminder that there is no silver bullet in managing influenzaa multipronged approach is key.
There are two anti-viral medications currently available for the treatment and prevention of influenzaoseltamivir (trade name Tamiflu) and zanamivir (Relenza). Both effectively treat influenza if given early in the course of illness, and appear to significantly reduce serious complications such as pneumonia. Anti-virals also help control the spread of influenza when administered preventively.
Unfortunately, use of anti-virals for seasonal influenza remains low. In a review in the April 23 issue of the Journal of the American Medical Association, Paul Glezen wrote: The use of these preparations against seasonal influenza should be strongly encouraged by public health officials so that clinicians will be familiar with the advantages and disadvantages. Indeed, the CDC has done just that, identifying anti-virals as part of its Take 3 approach to managing influenza.
We must learn how to use these medications effectively and also better understand the potential emergence of resistance. This season, the CDC reported high levels of resistance to two older anti-virals called amantadine and rimantadine (all but one of H3N2 seasonal type A viruses and 11% of H1N1 type A viruses), and recommended against their use. While overall resistance to oseltamivir remains low, the CDC detected reduced susceptibility among 10.2% of H1N1 viruses.
Anti-viral medications will be key in the early days of a pandemic outbreak, since development of a vaccine could take six to eight months. Development of new therapies is also under way, which would give us more options to fight the virus.
Vaccines and drugs alone are not enough. While modern science gives us an advantage, nonpharmaceutical interventions remain critical in influenza management.
Quarantine, travel restrictions and social distancing were effective during previous pandemics. One analysis of the 1918-19 influenza pandemic published in JAMA found that voluntary isolation and quarantine, school closures, and other forms of social distancing reduced disease spread and saved lives, particularly when used in combination. Cities that responded early, and sustained their response, had lower death rates than those that intervened later.
This season, school closings were implemented in states such as Colorado and Massachusetts to contain the spread of seasonal influenza within communities. During a pandemic, the CDC recommends closing schools and limiting social contact as a way to minimize transmission.
Pandemic influenza has fallen out of the headlines, and a certain degree of pandemic fatigue and planning lethargy has set in. But the threat itself is not diminished. At the annual general assembly of the World Health Organization last month, Margaret Chan, director general of the WHO, stated that the threat (of a pandemic) has by no means receded, and we would be very unwise to let down our guard, or slacken our preparedness measures.
While we may not be able to predict what virus will cause the next global influenza pandemic or when, it will happen. The race to prepare is on.
Richard Whitley is professor of pediatrics, microbiology, medicine and neurosurgery at the University of Alabama Birmingham Center for Biodefense and Emerging Infections. He recently co-chaired Seasonal and Pandemic Influenza 2008, an annual conference where global flu experts convene to discuss developments in combating influenza.