Fever in Common Infectious Diseases

Infection of the upper airways is very common and is the most common acute illness evaluated in the outpatient setting. The infection is usually caused by viruses including rhinoviruses, influenza viruses, parainfluenza and respiratory syncytial viruses. Influenza is the only viral infection preventable by vaccination and occurs predominately during annual winter epidemics. Bacterial infection such as acute rhinopharyngitis is uncommon and usually presents with either persistent symptoms of an URTI lasting over a week or worsening course after initial improvement or acute onset with high fever and inflammatory changes confined to the pharynx. Fever is common in both bacterial and viral gastroenteritis. High fever is commonly present in many bacterial causes (e.g. Shigella, Salmonella, Shiga toxin-producing E. coli). Fever is often absent or low-grade in other diseases (e.g. enteropathogenic E. coli, cholera). Other febrile conditions cause diarrhoea and need to be differentiated. Fever in CNS infection is the most common presenting symptom in children beyond the neonatal age owing to the presence of inflammatory mediators, particularly IL-1 and TNF in the blood or within the CNS. In MCD, fever was the first symptom in children younger than 5 years and 94% developed fever at some point. Viral exanthems are common causes of febrile illness in children. More than 50 viral agents are known to cause a rash. Historically, exanthems were numbered in the order in which they were differentiated from other exanthems. Thus the first was measles; second, scarlet fever; third, rubella; forth, so-called Filatov-Dukes disease (no longer recognized as an entity); fifth, erythema infectiosum; and sixth, exanthema subitum. As more exanthems were described, numerical assignment became impractical.