Voluntary HIV tests should be offered to all patients attending clinics, for whatever reason, in countries where AIDS is widespread, the World Health Organisation said on Wednesday.

Elsewhere, testing is recommended for all patients attending selected facilities, such as antenatal or sexual health clinics.

Issuing new guidance to governments, the global body said a major expansion in testing was essential if the world was to beat the HIV/AIDS pandemic, which has killed more than 25 million people in the past quarter of a century.

The AIDS virus today infects around 40 million worldwide, most of them in sub-Saharan Africa, where just 12 percent of men and 10 percent of women know their HIV status.

“This is radical in the sense that things have to change,” WHO HIV/AIDS director Kevin De Cock told Reuters.

“Across the world, people with HIV are flowing through healthcare settings, not being diagnosed and not being offered the advantages of knowing their status.”

Drugs can hold HIV at bay and keep patients alive, but unless people know they are infected they will not seek treatment. They are also more likely to infect others.

The WHO says less than 20 percent of HIV-positive people in low and middle-income countries know they are infected.

The situation is better in rich countries, yet even in United States an estimated 25 percent of infected people are unaware they are carrying the virus, while in Europe the rate is around one third.

Until now, most testing has been “client-initiated,” with individuals having to actively seek an HIV test. But in future, the WHO wants to see “provider-initiated” testing, which should become the norm at health centers, unless a patient declines.

Universal coverage is recommended for countries gripped by a generalized epidemic, where the HIV prevalence rate in pregnant women is consistently above 1 percent - which includes most of Africa and parts of the Caribbean - while targeted testing is suitable for concentrated or low-level epidemics.

Some countries in Africa, such as Botswana and Kenya, have already started broad testing programs and De Cock said the price of around $1 for a simple, rapid test meant that cost should not be an insurmountable obstacle.