There are now 6,497 confirmed cases of influenza A(H1N1) infection worldwide, a situation that Keiji Fukuda, Interim Assistant Director-General of the World Health Organization, says "is serious and that requires close monitoring." The WHO, however, is maintaining its pandemic alert at the Phase 5 level, which means that a pandemic is imminent but not yet present.

To date, Mexico has reported 2,446 cases with 60 deaths and the United States has reported 3,352 cases and three deaths. Canada reports 389 cases and one death. Costa Rica reports eight cases and one death. The following countries have reported confirmed cases with no deaths: Argentina (1), Australia (1), Austria (1), Brazil (8), China (4), Colombia (7), Cuba (1), Denmark (1), El Salvador (4), Finland (2), France (14), Germany (12), Guatemala (3), Ireland (1), Israel (7), Italy (9), Japan (4), Netherlands (3), New Zealand (7), Norway (2), Panama (29), Poland (1), Portugal (1), Republic of Korea (3), Spain (100), Sweden (2), Switzerland (1), Thailand (2), and the United Kingdom (71).

Speaking at a news conference, Dr. Fukuda announced the continuation of the Phase 5 designation and that, "if we see changes in the severity we will let the world know about that". His comments would seem to imply that severity is a consideration in declaring a flu epidemic to be a pandemic. Any such suggestion is quite false. If an infection spreads worldwide, then it is a pandemic regardless of how severe or mild an illness it produces – that is all the term means. The inherent virulence of a virus, that is, its ability to produce severe illness and death, is an entirely separate matter.

Fortunately, while H1N1 seems well on its way to becoming a pandemic, it does not appear to be an especially virulent form of flu. We cannot be certain yet how high a level of mortality will occur among cases of this new swine-origin flu, especially if there is a second wave of infections this winter. In the meantime, there are important decisions regarding prevention measures that need to be made and implemented very soon.

At present, the world’s leading vaccine makers including GlaxoSmithKline, Sanofi-Aventis, Novartis and Baxter International, are awaiting guidance from the WHO on whether they should manufacture vaccine for the H1N1 virus instead of for seasonal flu. A panel of vaccine experts convened in a teleconference by the WHO last Thursday, however, did not reach a conclusion about whether such a switch should take place, or whether the H1N1 strain should be included in the mixture of the seasonal flu vaccine, according to Dr. Fukuda. "There will be additional meetings," he said after that conference ended with "no big decisions, no pronouncements."

Most flu vaccine companies can only make one vaccine at a time. Production takes months and it is impossible to switch halfway through if health officials make a mistake. Vaccine makers could make limited amounts of both seasonal flu vaccine and H1N1 vaccine -- although not both at the same time -- but they cannot make massive quantities of both because that would exceed their manufacturing capacity of about two-billion vaccine doses. So it is essential that a decision be made soon over whether to manufacture seasonal flu vaccine or an H1N1 vaccine.

An important factor in weighing the choices is the fact, often overlooked by the public and politicians, that seasonal flu is also responsible for substantial mortality. Every year, seasonal flu kills up to a half-million people around the world and about 35,000 in the U.S. alone. Therefore, shifting resources away from seasonal flu vaccine to an H1N1 vaccine is not a risk free choice.