Most healthy people who are infected by HCMV after birth have no symptoms. Some develop a syndrome similar to infectious mononucleosis or glandular fever, with prolonged fever, and a mild hepatitis. A sore throat is common. After infection, the virus remains latent in mononuclear cells without causing detectable damage or clinical illness for the duration of the person's life. Overt disease can occur and is a particular challenge for immunocompromised individuals and newborns. HCMV is the leading infectious cause of congenital birth defects in developed countries, affecting 0.3–2.3% of newborns worldwide. Congenital HCMV infection can result in severe developmental abnormalities, including hearing loss, vision impairment, and neurological disorders.