Primary HIV infection is an acute contagious disease caused by the human immunodeficiency virus (HIV). It is characterized by non-specific signs and symptoms which develop after an individual is exposed to the virus and can manifest until he/she develops antibodies. The diagnosis of the disease can be missed or mistaken due to the flu-like symptoms and inability of laboratory tests to detect specific antibodies to the virus.
Primary HIV infection, also known as an acute retroviral syndrome or acute HIV infection occurs within three to four weeks  after a person is infected with the human immunodeficiency virus and can last for up to three months until the HIV-specific antibodies develop .
A few patients with this infection are asymptomatic but a majority of them develop flu-like signs during this period . These are usually non-specific  and include fatiguability, fever, myalgia, sore throat, and skin rash  with constitutional symptoms like malaise, anorexia, loss of weight, diarrhea, and tender lymphadenopathy, typically in the inguinal region. A headache, neck stiffness, encephalitis, aseptic meningitis and cranial nerve V or VII involvement can also be the presenting manifestations in some patients. Other neurological features include demyelinating polyneuropathy and mononeuropathy leading to wrist drop or foot drop.
A characteristic maculopapular rash on the proximal aspect of the extremities and trunk is noticed. Oral thrush, hairy leukoplakia, and aphthous ulcers may be seen on oropharyngeal examination. In addition, orogenital lesions due to herpes simplex or reactivation of herpes zoster with vesiculation can occur.
The diagnosis of primary HIV infection can be challenging. A high index of suspicion in those at risk e.g. intravenous drug users, sex workers, men who have sex with men, transgender individuals and those indulging in unprotected intercourse with multiple sexual partners, is essential to diagnose the condition. A detailed history and thorough physical, oropharyngeal, and neurological examination will provide clues to the presence of the infection. Oral candidiasis, hairy leukoplakia, herpes lesions and aphthous ulcers can be diagnosed clinically. Scrapings from oral ulcers for detection of fungal hyphae and a Tzanck test can also be performed to confirm candidal and herpetic infection respectively.
A complete blood count may indicate anemia and thrombocytopenia while a rapid viral load test typically shows an elevated level of HIV along with a decrease in CD4 count. Enzyme-linked immunoglobulin M (IgM) assays help to detect HIV within 23 to 25 days after the initial infection    and p24 antigen can be detected within 20 to 30 days . If the initial test is negative, then a second test can be ordered within three months .
Testing for drug resistant strains is recommended if HIV infection is detected . In patients with persistent lymphadenopathy, serology tests for cytomegalovirus and Epstein-Barr virus should be performed. If liver transaminases are elevated, hepatitis A, B, and C infection should be ruled out with serological tests.