Buying Time—The Immune System Determinants of the Incubation Period to Respiratory Viruses

Hermesh, Tamar; Moltedo, Bruno; López, Carolina B.; Moran, Thomas M.

The incubation period is a helpful definition that describes the time between virus infection and the onset of symptoms. Based on new findings, we propose a model that describes a mechanism of the delayed symptoms (innate immune response) that is likely common to almost all known respiratory virus infections (Figure 2 ). The delayed rise of the innate immune response to a respiratory virus is explained by the suppression of immunity by the viral antagonist in vivo. The "stealth phase" is terminated by an initiating event or breakthrough that triggers type I IFN and other cytokines that serve to stimulate cells before they are infected. Type I IFN primed cells are protected from viral antagonism allowing the innate immune response to proceed. Much work must still be done to determine the factors, the sequence of events, and cell types that are relevant to accomplish the end of the incubation period.