Undernutrition can affect the invading microorganism.

Undernutrition or malnutrition adversely affects host defenses against many invading microorganisms, thereby increasing the severity of infection. Studies of RNA viruses (e.g., coxsackievirus B and influenzavirus) have shown that selenium or vitamin E deficiency in mice increases disease severity and results in stable genomic changes in the virus that increase virulence. Changes in H3N2 influenzavirus were predominantly in the ordinarily stable M1 matrix protein. Whether this represents selection of already-existing variants or direct effects on viral RNA is unclear. Related questions include whether undernutrition in persons who acquire infection with influenzavirus H5N1 could promote genomic changes during infection that result in greater virulence and higher case-fatality rates, and whether undernutrition could help create the multiple mutations needed to instigate human-to-human transmission. These possibilities emphasize the importance of alleviating world poverty and malnutrition. In addition, these findings suggest that the neglected area of undernutrition affecting invading microorganisms merits intensive investigation in humans and experimental models.