Swine Flu Update

Electron micrscope image of H1N1 virus

I recently witnessed 2 cases of swine (H1N1) flu that resulted in different outcomes. Both patients were of about same age, 40 and 41. The younger patient smoked cigarettes and likely had underlying lung disease; the other did not. Both were admitted to a hospital on the same day. Both had high fever. The smoking patient had to be intubated and be placed on ventilator shortly after her admission. The non-smoking one managed to get by. Initial rapid flu tests were negative for both patients. Oropharyngeal PCR tests, however, were positive for both. Three days later the smoking patient died, but the non-smoking one was discharged home in stable condition.

Center for Disease Control recently evaluated rapid flu tests, also known as screening tests, and found that these tests had low sensitivity (40%-69%). Low sensitivity means a negative test shows no H1N1 virus only in 40% to 69% of tested patients. As a result, WHO recommends antiviral medications such as Tamiflu be considered for patients with higher risks such as pregnancy, pneumonia, rapid progression to respiratory distress, or other underlying diseases. Meanwhile, PCR assay test should be used to make a definitive diagnosis. The disadvantage of PCR test is that it takes longer, usually 2-3 days in the US, to obtain final result.