In the 34 years since scientists first identified HIV, much has changed. What was once an almost certain death sentence is now considered a chronic but manageable health condition and, in fact, preventable. This glossary of terms illustrates the changes in prevention and care.

HIV positive: This means tests detected the antibodies for HIV. Antibodies are specific proteins produced by the body to combat foreign items in the body such as viruses and bacteria. An adult person only HIV antibodies if the virus has infected that person.

HIV negative: This means tests have not detected the HIV antibodies. It could mean that a person does not have an infection or that the infection is in the early stage and that the body has not fully responded and developed the telltale antibodies (which takes about three weeks).

Viral Load: This test measure level of virus in the blood. The test can detect as few as 28 viral particles per milliliter of blood. The higher the viral load, the more infectious a person is as well as the more likely the virus will cause significant damage to the immune system.

Undetectable: This means the person is living with HIV but has successfully suppressed the virus through medication. It refers to a measure of viral load that cannot detect the virus in the blood. It does not mean the person is not still infected with the virus. Rather, it means the virus is well controlled in the body. Recent studies have found a person who has an undetectable viral load is unlikely to transmit their infection to sexual and needle sharing partners.

TasP: This is an abbreviation for Treatment as Prevention. Scientists have discovered that when a person is on medications and has an undetectable viral load, they are highly unlikely to transmit the infection. As a result, the CDC and state and local health officials have moved towards encouraging people living with HIV to get on treatment for two reasons. First is better long-term health outcomes for the person with HIV, and the second is the reduction in the risk of transmission to sexual and needle sharing partners.

PrEP: This is an abbreviation for Pre-exposure Prophylaxis. It is the newest weapon in prevention of HIV and involves taking a specific two-drug combination anti-HIV pill daily. Studies have found that when taken daily, the drug is at least 92 percent effective in preventing a person from becoming infected with HIV. A model of the drug’s efficacy has estimated it may be as effective as 99 percent in stopping a person from contracting HIV. The CDC in 2014 released a broad new clinical guidance to encourage broad application of the drug in high risk groups.

HIV Incidence: This is the number of new cases of HIV in a given year. In 2014, Ingham County had an incidence of 25.

HIV prevalence: This is the number of people living with HIV — including those who have not been identified — per 100,000 people. Ingham County’s HIV prevalence was 175. Clinton County’s was 48, while Eaton County’s was 53. Ingham County has the highest prevalence rate outside of Detroit, according to data from the Michigan Department of Health and Human Services. The City of Detroit has a prevalence of 800 cases per 100,000 people.

Treatment Cascade: This refers to the continuum of care for people living with HIV. It starts with an estimate of the number of people infected, how many know they are living with the virus, the number who have accessed medical care, are engaged in continued care and the number of people who have achieved a suppressed viral load. It helps public health and medical providers create programs to reduce the transmission and prevalence of HIV in communities.

HIV Disease: HIV, medically, is no longer broken into HIV infection and AIDS. All clinical diagnoses are now rated on a three-stage process. What was traditionally referred to as AIDS is now HIV Disease Stage 3. Despite significant improvements in medical care that often results in restoration of immune system functions, once a person is diagnosed as HIV Disease Stage 3, they will remain in that category until death.