Chances are, you’ve had a respiratory infection. From the common cold to strep throat, these infections run the gamut from mild inconveniences to near-deadly for vulnerable individuals. While viral respiratory infections are common, there aren’t any simple, inexpensive diagnostic tests to determine whether a virus is the cause of an infection. However, two Yale researchers, Marie L. Landry and Ellen F. Foxman ‘93, have worked to change this by identifying a way to determine if a respiratory illness is caused by a virus.
“We looked at biomarkers, or molecules the body makes, that signify that it’s fighting a viral infection,” Foxman said. “Instead of looking at the infection itself, we were looking at molecules that the body makes when it’s fighting all sorts of viral infections in the airway.”
The first study looked at the transcription levels of three mRNAs (CXCL10, IFIT2, and OASL) to determine which genes are “turned on” the most when the body is fighting a viral infection, and subsequently how well those genes predict a viral infection. mRNAs are the molecules the body produces as a direct result of genes being expressed, so measuring mRNA provides a direct link to the gene. Astonishingly, a test combining levels of the three mRNAs was 97 percent accurate in predicting viral infection. The second study measured two proteins produced by the previously identified mRNAs, CXCL11 and CXCL10, and also found a high correlation between the proteins and viral infection.
These results are remarkable not only in their accuracy, but also in their implications for diagnostic testing. While perhaps unnecessary for generally healthy individuals with a cold, this diagnostic could be helpful for patients with complex health issues that make it difficult to determine if, for instance, a fever is caused by the flu or an organ being rejected by the body. Foxman also noted her approach could be used to identify patients infected with new viruses, and she hopes this diagnostic test will be broadly implemented soon.
 Interview with Dr. Ellen Foxman, Yale Department of Laboratory Medicine, interview on 1/30/18
 “Antiviral response in the nasopharynx identifies patients with respiratory virus infection.”, M. L. Landry and E. F. Foxman, Journal of Infectious Diseases, 2017 [https://academic.oup.com/jid/advance-article/doi/10.1093/infdis/jix648/4743270]