Though some Chinese cities now use advanced testing technologies and equipment to ensure the safety of donated blood, more support from local governments is vital, health experts said.

According to a recent report by the central blood bank in Dongguan, Guangdong province, the number of blood donors diagnosed as HIV-positive has been rising in recent years.

Ten of every 100,000 blood donors from 1999 to 2003 were diagnosed as carriers of the HIV/AIDS virus. But from 2008 to 2012, 34 of every 100,000 were carriers.

The Dongguan report concludes that HIV/AIDS is beginning to spread among residents of the Pearl River Delta city.

"The blood samples are immediately destroyed when the donors are diagnosed as HIV-positive," said Zou Wentao, deputy director of the Dongguan city center blood bank.

But Zou cautioned that there is a period after a person is infected during which they won't test positive. This is called the "HIV window period" and it can last from 11 days to three months, depending on the testing agent and equipment.

To ensure the safety of blood donations, cities such as Dongguan and Beijing have turned to advanced testing technologies such as nucleic acid amplification test, said Zou, who is also an expert at the blood quality control center of Guangdong province.

"By using the NAT technology, HIV/AIDS can be diagnosed in six to 12 hours after the 11-day window period," Zou said.

The testing agent is also widely applied to the diagnosis of hepatitis B and hepatitis C infections.

"With the traditional testing method, which tests antigens or antibodies, the window period of HIV/AIDS is around three months. The window period is shortened to around 11 days with NAT, with which the existence of virus itself is also tested," he said.

As a last line of defense, Dongguan has set up a blood quality supervision group, the first of its kind in the country, to conduct sample testing of blood from donation centers.

Zou said advanced testing technologies serve as the primary guardian against infections, Zou said.

Wang Hongjie, deputy director of the Beijing Red Cross Blood Center, agrees with Zou.

In practice, NAT has proved most efficient in the detection of hepatitis B, a virus much more prevalent than HIV/AIDS in China, Wang said.

"Since our center started the NAT test in 2011, most of the blood donations we have prevented from being used were HBV positive," Wang said.

But the reagent used in the NAT test costs 80 yuan ($12.80) per person, much more expensive than the reagent used in the traditional method, which costs less than 20 yuan per person. To make up for the gap in costs, blood donation centers need government support to conduct NAT tests, Wang said.

Contact the writers at [email protected] and [email protected]

He Baoqi contributed to this story.

(China Daily 06/26/2014 page4)