Blog Post: Dr. John D. Cahill, M.D. May 7, 2009

Expert Commentary: Dr. John D. Cahill, M.D. June 12, 2009

With swine flu spreading to a number of countries, most of them developed and with fairly comfortable supplies of antiviral drugs, it might seem that the world is in pretty good shape to suppress a seriously lethal pandemic.

Although these drugs appear effective against this strain, it should be remembered that theses drugs are not necessarily indicated for cases of low possible exposure or less severe cases of swine influenza. They should be reserved for more severe infection, those with underlying significant medical problems, and if there is a clear high-risk exposure to an infected individual. Indiscriminant use of these drugs could lead to rapid resistance and decrease their effectiveness.

Also of concern is the fact that most nations with antiviral stockpiles have invested in only a single drug – oseltamivir (Tamiflu). Because of this over-reliance on one antiviral, the flu bug could develop resistance to the drug. This new strain could then spread and immeasurably complicate efforts to halt the evolution of a pandemic.


One potential solution to this problem could be to provide affected nations with small supplies of a secondary antiviral drug that could be used as an initial weapon to slow the spread and reduce
the severity of the infection. Once that were achieved, and the supply of the secondary medication exhausted, the primary antiviral (oseltamivir) could be vigorously introduced against the remaining flu cases in which the virus was still vulnerable to oseltamivir.


New research suggests this approach could, indeed, work. Joseph Wu, of the University of Hong Kong, working with researchers in Britain and the United States, used a mathematical model to represent the growth of a flu pandemic. The scientists found that using not oseltamivir but a secondary drug to treat only the first 1 percent or so of the population in a local epidemic, was effective in producing a considerable delay in the development of resistance to oseltamivir. The model showed that this delay in resistance development reduced the pandemic’s severity in both local populations and those in remote areas of the world where the contagion would later spread through air travel.


Regarding the current swine flu outbreak, the secondary drug could be zanamivir (Relenza), the only other approved drug that’s been found to be effective against the new H1N1 strain.

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