Final answer:
True, about 20 percent of people with HIV are unaware of their infection, due to the virus being asymptomatic for long periods and the need for confirmatory testing after initial screenings.
Step-by-step explanation:
The statement that about 20 percent of all HIV positive people do not know they have the infection is indeed true. Despite advancements in awareness and testing, a significant portion of those infected with HIV are unaware of their status. This can be attributed to the fact that HIV can be asymptomatic for a long period, with a clinical latency stage that can last up to a decade or even longer in some cases. Moreover, the global prevalence of HIV remains high, with Sub-Saharan Africa being home to nearly 70 percent of the world's HIV-positive cases.
It's crucial for individuals to undergo testing, especially since initial screenings like the ELISA test can sometimes yield false results, necessitating confirmatory tests such as the western blot or PCR. This multistage testing is crucial to ensure an accurate diagnosis. Hence, the high number of undetected cases underscores the importance of regular HIV screening.