Bacterial superinfection of the lower respiratory tract can result in pneumonia and bronchitis. The usual pathogens are Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus. Viral pneumonia is a serious life-threatening complication, more common in adults and immunocompromised patients. It generally appears 3 to 5 days into the course of the illness and is associated with tachypnea, dyspnea, cough, and fever. In adults it can be asymptomatic.
Neurologic disease can occur before or after the acute infection.
Neurologic abnormalities are manifested as acute cerebellar ataxia or encephalitis. Cerebellar ataxia is a benign complication that is thought to be due to postinfection demyelination. Resolution occurs within 2 to 4 weeks. It is estimated to occur in 1 in 4000 cases, among those younger than 15 years old. It usually appears within one week of the exanthema but it can appear 21 days after the onset of rash.