Fan Zhenbang and Pan Zhongfeng, from Shuangmiao in Henan province, were taken into custody on July 8 and will be detained for 30 days for "assembling a crowd to stir up trouble," said Li Dan, a Beijing-based activist.
Tens of thousands of villagers in Henan were infected by an unsanitary blood-buying industry in the 1990s, making it the country's hardest-hit province.
Fan and Pan were part of a group of 20 or 30 villagers who in March broke into a local hospital, where they say they were infected after selling blood, Li said.
The group had appealed to a local court to investigate their infections, but the court refused, he said.
"The villagers were trying to get the government to admit that they had been wronged and hoped that they would get a fair answer to what had happened to them," said Li, who set up a charity helping AIDS orphans.
The villagers went to the hospital and took equipment from the building in protest, he said. Police stood by and made a list of the items that were taken but did not stop the protesters or arrest them, Li said.
He said Fan and Pan were likely arrested because attention has recently been focused on China's fight against AIDS and authorities were trying to discourage demonstrations.
No one answered the telephone Sunday at the police station in Zhecheng (search) county, where Shuangmiao village is located. County government officials said they were "not clear" about the case.
China says it has some 840,000 people infected with HIV and about 80,000 with full-blown AIDS. But the U.N. AIDS agency says the true figures could be much higher and warns that 10 million Chinese could be infected by 2010.
Beijing has become increasingly open about its AIDS epidemic after years of denial and has promised to provide free testing and counseling for those who seek it and free anti-retroviral treatment for the poor.
Still, people demanding better treatment and care are routinely arrested.
A couple in Henan was arrested July 11 for protesting the closure of their children's school, which served pupils whose parents had the AIDS virus or had died, activists say.
In April, at least six people with HIV/AIDS were detained in Henan after seeking help from local officials, according to Amnesty International.