New fears of an influenza pandemic

November 1, 2005

Influenza is a seasonal disease, and autumn is when you gear up to immunize your patients (and yourself!) against a predictable antagonist. For some years, the big worry has been the availability of vaccine. This year, supplies are expected to be sufficient with four manufacturers in the field, although one-Chiron-is still trying to surmount manufacturing problems. Enough supply uncertainty lingers for the Centers for Disease Control and Prevention (CDC) to have listed priority groups for earliest vaccination-a list (now expired) that included infants 6 to 23 months old.

Influenza is a seasonal disease, and autumn is when you gear up to immunize your patients (and yourself!) against a predictable antagonist. For some years, the big worry has been the availability of vaccine. This year, supplies are expected to be sufficient with four manufacturers in the field, although one-Chiron-is still trying to surmount manufacturing problems. Enough supply uncertainty lingers for the Centers for Disease Control and Prevention (CDC) to have listed priority groups for earliest vaccination-a list (now expired) that included infants 6 to 23 months old.

This year, however, something new has been added to the mix: An epidemic of an influenza strain (H5N1) that infects birds is spreading rapidly from Asia to Europe, showing up most recently in Turkey, Romania, and Greece. So far, only a very small number of human beings have been infected with this strain, and almost all caught the disease from poultry they had handled. Person-to-person transmission does not seem to have occurred. But the great fear is that this avian flu strain will mutate or blend with another flu strain and become capable of infecting human beings with transmissible disease.

That fear was buttressed by the unraveling recently of the genome for the strain on influenza virus that caused the 1918 pandemic, which killed an estimated 20 million to 50 million people worldwide. The 1918 pandemic virus, this new research established, was also an avian strain to which human beings had no prior immunity, and that leaped from birds to people. The genetic makeup of the 1918 virus is disturbingly similar to the H5N1 avian flu virus now sweeping through domestic poultry flocks and wild migratory birds. All this raises the possibility of a global influenza pandemic.

Stockpiling of antiviral drugs that have shown some effectiveness against avian influenza lags far behind projected needs: By the time the federal government got around to ordering Tamiflu (oseltamivir) from Roche, the drug's only manufacturer, countries that had placed orders early on were at the top of the distribution list. At present, supplies are limited; if the United States is lucky, Roche will produce enough for our needs before the pandemic hits-if it hits. Poor countries of the world are out of luck: The price of this patent-protected drug is too high for them to afford. One ray of hope is the claim by generic drug manufacturer Cipla, based in India, that the company will shortly be able to produce a cheaper, generic version of oseltamivir for sale in the developing world.