What kind of bug have you got?

CDC Influenza Laboratory/Wikimedia Commons

The H1N1 influenza virus. View full image

Is your current miserable illness viral or bacterial? Often, we guess wrong and treat a virus with antibiotics—which have zero effect on viruses. But two Yale School of Medicine researchers may take out the guesswork. In experiments that started with cells grown in the lab, Assistant Professor Ellen Foxman ’93, senior author, and Professor Marie Landry were able to identify viral airway infections with 97 percent accuracy.

Their test makes use of the fact that when the body is battling viruses, it produces certain telltale molecules to defend itself. Foxman and Landry stimulated lab-grown cells from human nasal passages to simulate virus infection, then looked for molecules the cells started producing in large quantities. Three kinds of mRNAs (messenger RNAs) stood out. Next, they used swabs to collect and test mucus from patients with fevers, coughs, or other symptoms of respiratory infection. The levels of those three mRNAs in the samples enabled Foxman and Landry to find viral infections almost infallibly. 

The researchers also found two communication proteins (CXCL10 and CXCL11), either of which allowed them to rule in or rule out virus infections for two-thirds of the patients tested. 

The test worked even on patients who were immunosuppressed—possibly because ordinary respiratory-tract cells, not immune cells, make the proteins. The results are online in the Journal of Infectious Diseases.

With luck, a commercial quick-diagnosis version that could help prevent overuse of antibiotics may follow in the next five years.