The above shows only a possible scenario for a clinical and laboratory course of HIV-disease in a drug misuser. Considering the clinical events only a minority will experience a sero-conversion illness. Bacterial infections tend to be more serious in HIV positive drug misusers and they sometimes die from these infections. Such deaths would not be entered into the official AIDS statistics. Common opportunistic infections include Pneumocystis carinii pneumonia, disseminated cytomegalovirus infections, toxoplasmosis of the brain, cryptosporidial diarrhoea and oesophageal candidiasis. In addition there are a number of opportunistic tumours, particularly lymphomas, although the commonest tumour in homosexual men, namely Kaposi's sarcoma, is much less common in injecting drug misusers. Dementia, if it occurs, is usually in the last few weeks or months. A full definition of conditions defining AIDS is given in the Medical Morbidity Weekly Report 1987; 36 (supplement 15) 35-155.
Results of various laboratory tests after HIV infection may be quite variable. The T4 lymphocyte count is known to be depressed by the injection of street drugs, even without HIV infection, but may revert to normal after abstinence. There is a considerable amount of "noise" with the T4 count, but people with consistently low levels are at increased risk of developing opportunistic infections. In addition the reappearance of HIV antigen also has adverse prognostic significance, although, with current tests, it is only found in about two-thirds of AIDS patients.