Many factors influence the composition of the gut microbiota. Some of these are determined very early in life, and are not modifiable later in life, including individual genetic background, delivery method, and early infant feeding method (A). Other determinants are variable throughout life, and potentially modifiable, including diet and use of medications (B). Other factors are similarly variable throughout life, but potentially more difficult to modify, including persistent viral infection, the local environment and broader geographical environment (C).
HIV: Human Immunodeficiency Virus; SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2.