In this large study of patients diagnosed in PHI, we found that patients experiencing any of the following within 6 months of HIV diagnosis were more likely to experience more rapid progression of disease: one CD4 count <350 cells/mm3, 2 CD4 counts <500 cells/mm3, and/or experience of severe seroconversion illness (any of bronchitis, pneumonia, oral or pharyngeal candidiasis, thrombocytopenia, viral meningitis, bacterial meningitis, encephalitis, neuropathy). This evidence concerns the gene CD4 and viral encephalitis.