Chronic infection is common and can lead to cirrhosis and hepatocarcinoma. Transmission occurs through contaminated blood products, particularly after transfusions, and by other means. HIV preferentially infects cells bearing the CD4 surface receptor which comprise mainly T-helper cells. The immune suppression increases the susceptibility to secondary infections and cancer which eventually cause death. In addition to transmission by sexual contact, HIV can be spread through contact with contaminated blood and blood products.
Primary infection is usually sub-clinical and occurs in childhood.
The virus then remains latent in a sensory ganglion occasionally travelling back down the nerve to cause blisters. Virus is shed from the cold sores and may also be present in the saliva of an infant recovering from a primary infection. EBV is the cause of infectious mononucleosis in adults and can also lead to Burkitt's lymphoma in central Africa and New Guinea, and nasopharyngeal carcinoma in SE Asia. Infection during childhood is usually sub-clinical. CMV infections are often sub-clinical in both adults and children.