The primary route of entry for human<unk> es is the upper respiratory tract (mouth and nose).<unk>  A and B use "major" ICAM-1 (Inter-Cellular Adhesion Molecule 1), also known as CD54 (Cluster of Differentiation 54), on respiratory epithelial cells, as receptors to bind to. Some subgroups under A and B uses the "minor" LDL receptor instead.<unk>  C uses cadherin-related family member 3 (CDHR3) to mediate cellular entry. As the virus replicates and spreads, infected cells release distress signals known as chemokines and cytokines (which in turn activate inflammatory mediators). Cell lysis occurs at the upper respiratory epithelium. Infection occurs rapidly, with the virus adhering to surface receptors within 15 minutes of entering the respiratory tract. Just over 50% of individuals will experience symptoms within 2 days of infection. Only about 5% of cases will have an incubation period of less than 20 hours, and, at the other extreme, it is expected that 5% of cases would have an incubation period of greater than four and a half days. Human<unk> es preferentially grow at 32 °C (89 °F), notably colder than the average human body temperature of 37 °C (98 °F); hence the virus's tendency to infect the upper respiratory tract, where respiratory airflow is in continual contact with the (colder) extrasomatic environment.<unk>  C, unlike the A and B species, may be able to cause severe infections. This association disappears after controlling for confounders. Duly, amongst infants infected with symptomatic respiratory illness in low-resource areas, there appears to be no association between<unk>  species and disease severity.
Rhinovirus
Echovirus
Arbovirus
Respiratory syncytial virus
Human parainfluenza viruses
Poliovirus
Influenza B virus
Influenza A virus