Strains of HIV that are resistant to treatment are increasing in developing countries, especially in eastern and southern Africa, according to a new study published in the medical journal The Lancet.

This “could compromise the effectiveness of national HIV treatment programmes,” the study warned.

Resistance to treatment can be caused by people failing to stick to the strict rules on taking anti-retroviral drugs.

The study was carried out from 2001-11 on 26,102 patients from sub-Saharan Africa, Asia, and Latin America and also included World Health Organization data.

East Africa was deemed to be the region worst affected by a rising prevalence of drug-resistance strains of HIV, the virus that causes AIDS.

“The findings are of concern and draw attention to the need for enhanced surveillance and drug-resistance prevention efforts by national HIV treatment programmes,” the researchers said.

With monitoring, people who are showing resistance can be switched to a different drug regimen. Alternative treatment options must be made available for people showing signs of resistance in developing countries, according to the study.

The report comes as the US is hosting a major international AIDS conference. Governments are being urged not to cut funds for dealing with the HIV/AIDS epidemic in order to ensure that progress being made is not reversed.