In general, pathogens may be high-grade or low-grade. High-grade pathogens may be pathogenic in healthy individuals with normal immune status. Low-grade pathogens are usually pathogenic in persons with immunodeficiency. The pathogens that cause disease and the type of clinical disease they cause depend on the degree of progression of HIV infection and the associated extent of immunosuppression. High-grade pathogens (e.g. the pneumococcus, non-typhoid salmonellae and M. tuberculosis) can cause disease at any stage in the course of HIV infection. Low-grade pathogens (e.g. candida, Cryptococcus neoformans, toxoplasma, cytomegalovirus, Pneumocystis carinii and atypical mycobacteria) cause disease in the more advanced stages. Disseminated infections become increasingly common in advanced stages of HIV infection with more severe imunosuppression. The WHO clinical staging system for HIV infection and disease reflects these features. Diseases caused by low-grade pathogens and disseminated infections characterize stage 4 in adults and adolescents and stage 3 in children. Infections caused by the high-grade pathogens tend to be easier to diagnose and treat than those caused by the low-grade pathogens.
The spectrum of disease in HIV-positive persons varies among regions. Dominating the picture in sub-Saharan Africa are the high-grade pathogens (bacterial and mycobacterial) such as the pneumococcus, non-typhoid salmonellae and M. tuberculosis, which are endemic, highly associated with poverty, and intensely transmitted in overcrowded unsanitary environments.TB has become a leading cause of death among people with HIV infection, accounting for up to a third of AIDS deaths worldwide. There has also been recent recognition of the association between HIV infection and increased frequency of clinical malaria. In this region, some low-grade opportunistic pathogens are important (particularly cryptococcus and toxoplasma), but those that dominate the picture in the industrialized countries, such as Pneumocystis carinii and atypical mycobacteria, are relatively rare. Although the spectrum of disease in HIV-positive persons has not been as fully characterized in other regions, a similar pattern is likely to be seen throughout the developing world.
Nearly 90% of all HIV-positive persons live in developing countries in Africa and South-East Asia.Thus, worldwide, the main burden of disease in HIV-infected individuals arises from a limited number of common infectious agents, namely M. tuberculosis, pneumococcus and non-typhoid salmonellae. Diagnosis of these infections is usually possible at health centres or district hospitals. They are generally amenable to treatment with cheap, affordable and effective antimicrobials. For example, a course of TB treatment may cost as little as US$10 in some countries (although more in sub-Saharan Africa). Thus diagnosis and treatment of common HIV-related diseases due to high-grade pathogens are feasible and affordable. There is a need to strengthen the ability of general health care providers to diagnose and treat these diseases. This has the potential to dramatically decrease their contribution to HIV-related morbidity and mortality.WHO has developed an essential drugs list for the treatment of common HIV-related diseases. In many parts of the world the treatments for a variety of HIV-related infections (including herpes simplex virus, cytomegalovirus and atypical mycobacteria) and cancers (including Kaposi sarcoma and non-Hodgkin lymphoma) are more expensive and not yet widely available.
sexually transmitted infections
A person who has unsafe sex is at risk of several sexually transmitted infections (STIs). So a patient with one STI is at increased risk of having another STI. HIV is usually sexually transmitted. STIs other than HIV are common in TB/HIV patients. This section gives a brief account of the drug treatment of STIs. When you treat a patient with STI, also remember patient education, counselling, condom provision and partner management.
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