Clearing the Air Around Influenza

Unknowns

In the PIE study in the previous post, the lion's share of the pie went to unknown causes. Uncertainty is our staple diet when dealing with respiratory agents, especially viruses.

No one can tell clinically one agent’s signs and symptoms from another. Those who claim to be able to make a clinical diagnosis from signs and symptoms are charlatans. A positive laboratory test for, say, Coronavirus OC 43 makes it more likely that the bug is the cause of the symptoms, but OC43 does not cause distinctive features. In medicine-speak, no signs or symptoms are pathognomonic of OC 43 infection.

Another example of a PIE study was reported by Jain and colleagues in adults who required hospitalisation for community-acquired pneumonia between 2010 and 2012. The charts nicely illustrate the seasonal ups and downs of agent circulation and add the role of two common bacterial culprits, S. pneumoniae and S. aureus, which, unlike viridiae, respond to antibiotics.

Why are the majority of causes unknown?

Our t…