Iran is under mounting pressure to reveal the whereabouts of two of the nation's HIV researchers, who have been detained without charge since late June.

The brothers, Arash and Kamiar Alaei, have achieved international acclaim for their progressive HIV-prevention programme and were scheduled to speak about it at the 17th International AIDS Conference in Mexico City last month. Both were arrested before leaving the country. The men had collaborated with other scientists around the world, including some in the United States, and are not thought to have been politically active.

Arash Alaei has not been seen since June. Credit: H. ALLAM/KRT/NEWSCOM

Protests in their support were made at the conference. Since then, several human-rights organizations, including Physicians for Human Rights and Amnesty International, have called on Iran to abide by its international legal obligations to explain the arrests and allow the men access to lawyers and the right to contest their detention before a judge.

The call has been taken up by several scientific bodies, including the International AIDS Society, the Foundation for AIDS Research and the American Association for the Advancement of Science (AAAS), and thousands of scientists and physicians have signed an online petition at http://www.iranfreethedocs.org Barry Bloom, dean of the Harvard School of Public Health in Boston, Massachusetts, has also expressed his "deep concern" over the brothers' detention.

Kamiar, the younger of the brothers, holds a master's degree from the Harvard School of Public Health and was to have resumed doctoral studies at the University of Albany's School of Public Health in New York. Arash, former head of international education and research cooperation at the Iranian National Research Institute of Tuberculosis and Lung Disease, runs a clinic in Tehran.

HIV is a taboo subject in much of the Middle East, including Iran, but the brothers have helped to forge impressive prevention and treatment programmes — the country is now one of the few to distribute condoms and syringes in prisons, for example.