A hospital's request for blood from healthy female virgins has attracted public attention while raising awareness of the human papillomavirus, the primary cause of cervical cancer.

The notice, which requests the blood for HPV studies, appeared on online bulletin board systems at Peking University and Beijing Normal University last week.

Peking University Cancer Hospital is conducting studies of possible antibodies. The hospital said it would need 100 healthy female virgin college students from 18 to 24 years old as blood donors for the studies.

Some netizens denounced the request as promoting virginity worship, which they said is demeaning to women.

But hospital spokeswoman Guan Jiuping defended the request, saying the blood of virgins is medically necessary for the studies.

"It's in line with international practice to collect female virgins' blood samples, which serve as negative control substances in HPV research, given that the risk of contracting HPV is low among women who have never had sex," Guan said.

A serum antibody to HPV can come only from women who have never been infected, medical experts say. Unprotected sex is the most common risk factor of HPV infections.

"Too much attention to sensitive words like 'virgin' and 'sex' is not necessary in this context," Guan said.

But Guan said the hospital will improve its public communication skills for such unusual requests in the future.

Asked how the hospital will tell whether a prospective donor is really a virgin, Guan said hospital officials will take the donors' word for it.

Qiao Youlin, a cancer expert and a professor of oncology research at the Chinese Academy of Medical Sciences in Beijing, said many women get infected with HPV but the disease usually disappears without treatment.

There are many types of HPV, and only a few increase the risk of developing cervical cancer, he said.

Other risk factors of cervical cancer include poor diet, smoking and an impaired immune system.

Nationwide, 84 percent of cervical cancer patients had HPV infections of different kinds and about 15 percent of Chinese females have reported HPV infections, he said, citing previous research.

Statistics from the National Health and Family Planning Commission showed that cervical cancer was second only to breast cancer as the most common form of cancer among women.

Each year, more than 75,000 new cases occurred on the mainland, it said.

Lang Jinghe, a gynecologist at the Peking Union Medical College Hospital in Beijing, said the number of young women with cervical cancer has sharply increased over recent years.

But early diagnosis and treatment help control the disease, she added.

To aid in early detection, the central government launched a program in 2009 to give free cervical cancer screening to rural women.

Imported vaccines protecting women from HPV infection are in the process of getting approval to enter the Chinese mainland market.