Expert Opinion

David L. Cohn, MD, Associate Director of Denver Public Health and Professor of Medicine (Infectious Diseases) at the University of Colorado Health Sciences Center, offered his views on the current influenza A(H1N1) outbreak and potential implications for the future in an exclusive interview with Pulmonary Reviews.

• Is this current flu outbreak cause for alarm and panic?
• At this point, how severe is this epidemic?
• How bad can this situation eventually get and what is the likelihood that the current situation will become more serious?
• What comparisons can we make between this outbreak and those from the past, particularly the severe acute respiratory syndrome (SARS) and avian flu outbreaks?
• Will a vaccine be effective against A(H1N1) and will it be available in time for it to make a difference?
• Will this particular outbreak in any way affect the 2009-2010 flu season and if so, how?
• What can physicians do to better inform the public?

Pulmonary Reviews (PR): Is this current flu outbreak cause for alarm and panic?

Dr. Cohn: No. We are in the beginning of an epidemic that features a new variant strain of influenza A—2009 H1N1—with genetic elements from both swine and human species. Because most populations do not have prior existing immunity to this particular virus, there is concern there may be worse outcomes in terms of severity of illness and mortality. However, although initial reports from Mexico have suggested such outcomes, this has not occurred so far among cases in the United States. Much of the potential for alarm and panic is fostered by the unprecedented media attention.

PR: At this point, how severe is this epidemic?

Dr. Cohn: It is too early to tell the true severity of this epidemic. The experience in Mexico suggested considerable severity with higher mortality than expected from recent seasonal influenza. But reports from the United States and other countries have not shown the same degree of severity. A possible explanation is that there were many cases of mild illness due to H1N1 that were not detected or reported in Mexico, and therefore, the mortality rates actually are not that much higher than anticipated. Also, not all of the cases that occurred earlier in Mexico were confirmed as H1N1 virus, and some of these cases may represent other illnesses.

PR: How bad can this situation eventually get and what is the likelihood that the current situation will become more serious?

Dr. Cohn: I don’t have the crystal ball to accurately answer this question. It is likely there will be many more cases that will occur all across the United States and in several additional countries. Because of the active surveillance and intense scrutiny that is occurring, many more cases will be reported than there would be if it were “business as usual.” Hopefully, the situation will not become more serious in terms of morbidity and mortality. There is a possibility this epidemic will dampen in ensuing weeks and months, but may lead to a larger epidemic with the same strain next fall or winter [see below].

PR: What comparisons can we make between this outbreak and those from the past, particularly the severe acute respiratory syndrome (SARS) and avian flu outbreaks?

Dr. Cohn: This H1N1 epidemic is different than the prior SARS and avian flu outbreaks. SARS is caused by a different type of virus, coronavirus, a known cause of respiratory illness, but not known to cause severe pulmonary disease prior to the SARS epidemic. The high number of cases that occurred in China in 2003, and then other countries, came from an animal reservoir, with efficient transmission to and between humans before this new and initially mysterious disease was understood. Once transmission between humans was decreased by effective and strict infection control policies, the epidemic ended. Overall, about 8,000 cases were reported, with a 10% mortality rate.

Avian influenza virus (H5N1), although common in birds, does not appear to be efficiently transmitted from birds to humans, and even less so from human to human. Severe illness in humans has occurred, with a 60% mortality rate, but fortunately, these cases have been few in number and sporadic over the past few years—about 400 cases.

The current strain of H1N1 virus, like most strains of influenza, is highly transmissible between humans.

PR: Will a vaccine be effective against A(H1N1) and will it be available in time for it to make a difference?

Dr. Cohn: Once again, I don’t have the right crystal ball. However, given the current technology in virology and vaccine production, I’m optimistic that a safe and effective vaccine will be developed in a relatively short period of time, ie, months. Given the association of some cases of Guillain-Barré syndrome with the swine flu vaccine administered to millions in 1976—a matter that is still a topic of controversy with regard to causality—federal authorities will be judicious in testing the vaccine for safety prior to widespread implementation. It will likely be available for administration for next winter’s influenza season, but not for the current phase of the epidemic over the next several months, if it lasts that long.

PR: Will this particular outbreak in any way affect the 2009-2010 flu season and if so, how?

Dr. Cohn: It is possible that the current H1N1outbreak may diminish in the next several weeks or months, and then recur in the 2009-2010 season in North America. This “herald” phenomenon occurred prior to the Spanish flu pandemic of 1918-1919, which was caused by another H1N1 virus. However, as all influenza experts will tell you, predicting influenza is unpredictable. Or more clearly stated by a quote often attributed to my favorite epidemiologist (and Hall of Fame baseball player) Yogi Berra, but also to the Nobel Prize winning physicist Niels Bohr, “It is difficult to make predictions, especially about the future.”

PR: What can physicians do to better inform the public?

Dr. Cohn: In a situation like this with extraordinary media attention and input overload, it is very difficult not to give mixed messages to the public and create some element of cognitive dissonance. We say that cases in the United States are mild, but persons in Mexico have died. We say that transmission will probably not be sustained, yet we close a school to prevent further transmission. We advise health care workers to wear N-95 masks when caring for suspected cases, but we tell the public that masks are not necessary. While all of these messages are correct in the proper context, it’s easy for a concerned citizen to misinterpret them, sometimes out of context. There is no simple solution other than for us to give clear, accurate information based on the best evidence as it evolves—and to say, “We don’t know,” when we don’t.