Notifiable Diseases On-Line

AIDS

AGENT OF DISEASE

AIDS or Acquired Immunodeficiency Syndrome is caused by the human immunodeficiency virus (HIV). The virus infects cells of the immune system, resulting in damage to the system.

WORLDWIDE DISTRIBUTION

HIV/AIDS has been reported in virtually all countries. Worldwide, UNAIDS estimates that cumulative totals of approximately 8.4 million cases of AIDS and 29.4 million cases of HIV infection had occurred by the end of 1996. Over half of these HIV/AIDS cases have occurred in African countries located south of the Sahara Desert.

CANADIAN SITUATION

The Bureau of HIV/AIDS and STD estimates that as of the end of 1996, a cumulative total of 50,000 to 54,000 Canadians had been infected with HIV since the onset of the epidemic and that at that time 36,000 to 42,000 Canadians were living with HIV infection (including those with AIDS). This compares with previous estimates of 42,500 to 45,000 cumulative infections and an estimated 32,000 to 36,000 living with HIV infection by the end of 1994.

The number of new HIV infections in Canada in 1996 is estimated to have been between 3,000 and 5,000, which is higher than the estimated average number of 2,500 to 3,000 per year for the period 1989-94. The majority of this increase appears to be occurring among injection drug users (IDUs) and young gay men. However, available data also suggest that the rate of HIV infection among non-IDU heterosexuals (especially women) and Aboriginal peoples is increasing.

A recent decline in the number of AIDS cases reported to the Laboratory Centre for Disease Control may be linked to improved antiretroviral therapies and drug prophylaxis which delay the onset of the clinical symptoms defining AIDS. The Bureau of HIV/AIDS and STD and the Provinces and Territories have recently concluded that to better monitor the burden of HIV disease, surveillance be established for HIV including AIDS.

SYMPTOMS

The U.S. Centers for Disease Prevention and Control developed the first case definition ofAIDS in 1982; this was subsequently revised in 1987 and 1993. The case definition includes several "opportunistic infections" and cancers that are indicative of underlying immune dysfunction. Some of the more common opportunistic infections and cancers are pneumocystis pneumonia, disseminated herpes simplex, esophageal candidiasis, Kaposi's sarcoma, cancer of the cervix and non-Hodgkin's lymphoma. The proportion of HIV-positive individuals who go on to develop AIDS is not known. Approximately 15% to 20% of people infected with HIV will contract AIDS within 5 years, 50% within 7 to 10 years and close to 70% within 15 years. New advances in anti-retroviral therapy may increase the latency period between time of HIV infection and the development of AIDS.

PERIOD OF COMMUNICABILITY

The period of infectiousness is unknown; however, a person infected with HIV is presumed to be infectious (capable of passing the infection from one person to another) shortly after time of exposure to HIV until death.

HOW IT IS TRANSMITTED

HIV is transmitted from person to person through vaginal and anal sexual intercourse, the sharing of HIV-contaminated needles and syringes, and the transfusion of infected blood/blood-products. The virus has been isolated in saliva, tears, urine and bronchial secretions; however, infection has not been reported in persons who have had direct contact with these body fluids/secretions (though transmission is possible if the fluids are contamintaed with HIV-infected blood). The risk of infection through blood/blood product transfusion has been virtually eliminated in Canada with implementation of rigorous donor screening, HIV testing of donated units, effective heat treatment and other processes that ensure a safe blood supply. Infection with other sexually transmitted diseases, especially those that cause ulceration, may facilitate transmission of HIV.

An HIV-infected pregnant woman can pass the infection to her fetus. Furthermore, an HIV-infected mother who is breast-feeding can pass the infection to her infant.

PREVENTION/CONTROL

1. Confidential HIV testing and counselling services are available in all provinces. These services should be offered routinely in STD clinics, in family planning and prenatal clinics, in facilities that offer services to gay men and in communities where the prevalence of HIV is high.
2. All pregnant women should be counselled about HIV infection and should be offered HIV testing. HIV-positive women should be evaluated to assess their need for anti-HIV therapy.
3. Public and school health education programs should teach students about safer sex and build skills to negotiate safer sex with their sexual partners. Programs should address the needs and developmental levels of students who attend school and those who do not attend school.
4. Safer sex practices of wearing a latex condom for vaginal, anal and oral intercourse, and reducing the number of partners should be encouraged.
5. Injection drug users should be taught decontamination techniques or encouraged to use local needle exchange programs.