The saying "sleep tight, don't let the bugs bite" may sound much more frightening since tick bites have allegedly killed 18 people in Xinyang City, central China's Henan Province.

The 18 people were among 557 reported cases of suspected human granulocytic anaplasmosis (HGA), since May 2007. Most of the cases were found in Xinyang's Shangcheng and Guangshan counties and Shihe and Pingqiao districts, said the provincial Public Health Department in a statement.

Shangcheng County alone has reported 120 cases, including one death, between Jan. and Sept. 8. Among the 40 patients treated at the county People's Hospital, 17 have recovered while 23 remain seriously ill and have been transferred to higher level hospitals, said Wang Wei, a doctor at the hospital.

Patient Wu Xiuqin, 74, has now fully recovered and was chatting with her husband while Xinhua reporters interviewed her at home.

"After she became sick, her legs hurt so much that she couldn't stand up on her own. When the illness was in full force, she had a high fever and was unconscious," said Wu's husband, Xia Yunxing.

The disease is curable if treated soon enough. "Doxycycline and Ofloxacin are pretty effective in treating the disease." said Bao Faying, a doctor at the hospital.

But to pinpoint the cause of the infection is not easy. Of the 40 patients treated at the county People's Hospital, only 14 were sure that they had been bitten by ticks, while others have no clue whether they had been bitten or not.

Ticks are common in Shangcheng County and tick bites are not rare. So many people can't help wondering why only a handful of people in recent years became ill.

"Many of us have been bitten by ticks, both in the past and recently. So why are ticks bites infectious now but were not years ago?" asked Yang Chuanhai, a local villager.

Opinions are also divided as to whether it can be passed on from person to person. Xu Bianli with the provincial Center for Disease Control and Prevention (CDC) said , "People in close contact with the patient can also be infected."

However, Yu Fang, head of the Shangcheng County CDC said,"We can be pretty sure by now that it can not be passed on from one person to another."

The one person who died from the tick bite in the county in 2010 was Wu Dezheng, a rural doctor who did not seek treatment at hospitals above the county level.

The disease is often seen from May to Aug., and most people infected are aged between 50 to 70.

To probe the cause of the disease, the national CDC ordered Henan CDC to start monitoring the disease on May 31, said Xu .

Doctors at local medical clinics lacked knowledge about the disease since it was only identified in 2007, Xu told Xinhua. Monitoring the disease is still underway in Xinyang.

HGA reduces white blood cells and platelet counts in the blood, leading to organ failure and death.

"What we are doing right now is to hand out flyers to tell people if they have fevers, they must see a doctor as soon as possible," said Li Wenxue, a doctor at Hutai Village, Jingangtai Township of Shangcheng County.