A Chinese man nearing 80 years old was recently diagnosed with HIV and doctors say he probably caught the virus through having "frequent unprotected sex."

The case is the latest to support the opinions of experts who believe the virus is spreading fast among older Chinese men who have been largely neglected in the country's anti-AIDS campaigns.

The latest diagnosed man, whose identity has been concealed for privacy reasons, was admitted to Zhongnan Hospital in central Chinese city of Wuhan with a lingering fever. He was later found to be HIV positive, doctors at the hospital said Friday.

The man was widowed in his old age, has no record of blood transfusions, but had an "active unprotected sexual life," they said.

Gao Shicheng, a HIV specialist in Zhongnan Hospital, said that HIV/AIDS has started to infect middle-aged and elderly Chinese men who have little or no AIDS prevention knowledge.

Gao said this year alone he had diagnosed two senior men with HIV. Both contracted the virus through unprotected sex outside marriage.

A recent survey conducted by the Chinese Center for Disease Control and Prevention (China CDC) shows that among the new HIV infections, the percentage of people aged 50 or above with it grew from 7.8 to 14.9 percent. Most of them were male and were found to have contracted the virus through sexual intercourse.

Experts say the spread of HIV/AIDS has picked up among older Chinese men in recent years because China's senior citizens have become healthier, more open-minded about sex, and increasingly bored after retirement.

They called for anti-AIDS campaigns, which usually target young people with a focus on gays, sex workers, and rural migrants, to also cover seniors in a bid to raise the awareness of HIV/AIDS prevention knowledge.

China is fighting a hard battle to contain the spread of HIV/AIDS. According to a UNAIDS estimate, the country had about 740,000 people living with HIV by the end of 2009. Among them, 105,000 were estimated to have AIDS.

By the end of August 2010, the cumulative total of reported HIV positives in China was 361,599, with 65,104 recorded deaths.

Sex, other than blood transmission or mother-to-child transmission, has become the main channel for the spread of HIV in China.