Human Immunodeficiency Virus (HIV) is the virus that causes AIDS. It is transmitted when infected body fluids such as blood, semen or vaginal secretions come in contact with an uninfected person's broken skin or mucous membranes. Some examples of how transmission can occur are: vaginal, anal or oral sex, sharing of drug equipment, or an infected mother can pass it to her child during pregnancy, birth or breastfeeding. There are methods of preventing HIV transmission as well as therapies to manage the infection, but there is no cure.

AIDS stands for Acquired Immunodeficiency Syndrome. Some people with HIV will develop AIDS as a result of their HIV infection. AIDS is characterized by the development of certain infections and/or cancers, as well as a decrease in the number of certain cells in a person’s immune system. For more information, see the health unit's HIV and AIDS Fact Sheet.

HIV and AIDS are chronic diseases. Once someone is infected with HIV/AIDS, they have the infection and can infect other people for the rest of their lives. This means that the number of people who can spread the disease is not just the number of new cases (incidence) every year; it is also the number of existing cases (prevalence) from previous years. The provincial reportable disease database (iPHIS) counts incidence and not prevalence so the graphs below only show the number of new cases every year and not existing cases. Therefore, the number of people infected with HIV/AIDS in Simcoe Muskoka (who can spread the disease) is higher than the incidence in the graphs.

The following graph shows the number of new HIV and AIDS cases in Simcoe Muskoka between 2000 and 2008. There are many factors that influence how many cases are reported to the health unit, as explained on the Infectious Diseases page.

The following graph shows the incidence rate of new HIV and AIDS in Simcoe Muskoka and Ontario between 2000 and 2008. The 2000 to 2006 Ontario data was obtained from the most recent report from the Ontario HIV Epidemiological Monitoring Unit; 2007 and 2008 Ontario data are not currently available.

The incidence rate in Simcoe Muskoka is lower than the Ontario rate. There is some variability in the Simcoe Muskoka incidence rate, which means that there are multiple peaks and valleys and it is difficult to determine whether an increase is significant or whether it is within the expected range for this disease.