Respiratory Viruses’ Effect on All-Cause Mortality: Winter and Summer Pseudoseasonal Life Expectancy in the United States

Andrew Noymer, University of California, Irvine
Rahema Haseeb, University of California, Irvine

In temperate climates, mortality is seasonal with a winter-dominant pattern, due in part to cause-specific processes such as pneumonia and influenza. However, cardiac causes — which are the leading cause of death in the United States—are also winter-seasonal although it is not clear why. Interactions between circulating respiratory viruses (e.g., influenza, parainfluenza) and cardiac conditions have been suggested as a cause of winter-dominant mortality patterns. We propose and implement a way to estimate an upper bound on the magnitude of virus-attributable mortality. We calculate ‘pseudo-seasonal’ life expectancy, dividing the year into two six-month spans, one encompassing winter the other summer. During the summer when the circulation of respiratory viruses is drastically reduced, life expectancy is about one year longer. This suggests that even if viruses cause excess winter cardiac mortality, the population-level mortality reduction of (for instance) a perfect influenza vaccine would be much more modest than is often recognized.