Group I Primary HIV infection
Primary HIV infection (PHI) is also called the seroconversion illness or acute HIV infection. It represents the stage of infection after the acquisition of the virus when antibodies are developing as shown in Figure 4.1. Between 25% and 65% of people have been found to present with symptoms at the time of seroconversion. These can range from a mild, glandular feverlike illness to an encephalopathy. Common symptoms and signs are shown in Box 4.2. The severe symptoms are rare. The differential diagnosis of the mild seroconversion illness is protean and, without a high index of suspicion and a history indicating relevant risk behaviours or factors, the diagnosis may be missed.
The appropriate diagnostic tests for PHI, which should be carried out on serial blood samples, include tests for HIV antibodies and antigen. If these are negative and PHI is suspected, the definitive test is an HIV RNA PCR, which is the most sensitive test for the detection and quantification of the virus. Some of these assays are not routine and the interpretation of investigation results during PHI is difficult, therefore close consultation with colleagues in virology is strongly advised. At the time of PHI there is sometimes a high rate of viral replication, leading to a transient rise in HIV viral load and concomitant immunosuppression due to a short-lived fall in the CD4 count. This may result in manifestations of HIV disease which are normally seen later in the infection, for example oral candida. Diagnostic confusion as to the stage of HIV infection may arise, which can only be resolved by following up the patient for long enough to see the symptoms and signs resolve, HIV antibodies appear, the viral load fall and the CD4 count rise.
Treatment should be directed at alleviating any symptoms, and there is considerable interest in the possible use of antiretroviral agents at this time because the virus may be more susceptible due to the relatively low numbers of virus particles which can replicate, the reduced ability of the predominantly non-syncytium-inducing strains of virus to infect a wide variety of cell types and the enhanced immune response seen in PHI. Such treatment may decrease long-term damage to the immune system and delay or even prevent the development of AIDS.
However, if not started within 12–18 months of PHI the theoretical advantage may be lost and, in any case, has to be balanced against the uncertain outcome, drug toxicity, adherence difficulties and the possibility of developing resistant virus, limiting future treatment options.
Primary HIV infection (PHI) is also called the seroconversion illness or acute HIV infection. It represents the stage of infection after the acquisition of the virus when antibodies are developing as shown in Figure 4.1. Between 25% and 65% of people have been found to present with symptoms at the time of seroconversion. These can range from a mild, glandular feverlike illness to an encephalopathy. Common symptoms and signs are shown in Box 4.2. The severe symptoms are rare. The differential diagnosis of the mild seroconversion illness is protean and, without a high index of suspicion and a history indicating relevant risk behaviours or factors, the diagnosis may be missed.
The appropriate diagnostic tests for PHI, which should be carried out on serial blood samples, include tests for HIV antibodies and antigen. If these are negative and PHI is suspected, the definitive test is an HIV RNA PCR, which is the most sensitive test for the detection and quantification of the virus. Some of these assays are not routine and the interpretation of investigation results during PHI is difficult, therefore close consultation with colleagues in virology is strongly advised. At the time of PHI there is sometimes a high rate of viral replication, leading to a transient rise in HIV viral load and concomitant immunosuppression due to a short-lived fall in the CD4 count. This may result in manifestations of HIV disease which are normally seen later in the infection, for example oral candida. Diagnostic confusion as to the stage of HIV infection may arise, which can only be resolved by following up the patient for long enough to see the symptoms and signs resolve, HIV antibodies appear, the viral load fall and the CD4 count rise.
Treatment should be directed at alleviating any symptoms, and there is considerable interest in the possible use of antiretroviral agents at this time because the virus may be more susceptible due to the relatively low numbers of virus particles which can replicate, the reduced ability of the predominantly non-syncytium-inducing strains of virus to infect a wide variety of cell types and the enhanced immune response seen in PHI. Such treatment may decrease long-term damage to the immune system and delay or even prevent the development of AIDS.
However, if not started within 12–18 months of PHI the theoretical advantage may be lost and, in any case, has to be balanced against the uncertain outcome, drug toxicity, adherence difficulties and the possibility of developing resistant virus, limiting future treatment options.
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