Cause Of Mysterious Chinese Disease Solved In NEJM

STFS

Health
March 22, 2011

Dr. Xue-Jie Yu and colleagues have shown that a novel phlebovirus is responsible for seasonal disease outbreaks in six of China’s most populated provinces.

AsianScientist (Mar. 22, 2011) — In a breakthrough report featured by the New England Journal of Medicine, scientists from the United States and China have finally explained the deaths of large numbers of farmers in central China which were marked by high fever, gastrointestinal disorder.

Initial assessments by the Chinese Center for Disease Control and Prevention suggested that the disease had been caused by human granulocytic anaplasmosis, a bacteria transmitted by tick bites.

Funded by the China Mega-Project for Infectious Diseases and others, Dr. Xue-Jie Yu and colleagues proved that the original conclusion was incorrect, and it was a novel phlebovirus associated with fever and thrombocytopenia that has been responsible for seasonal outbreaks of the disease in six of China’s most populated provinces.

“We expected to find a bacterial infection behaving in an unexpected way — human anaplasmosis has a less than one percent fatality rate in the U.S., and it rarely causes abdominal pain or vomiting or diarrhea,” said Dr. Xue-Jie Yu of the University of Texas Medical Branch at Galveston, lead author of a paper. “Instead, we found an unknown virus.”

Researchers have dubbed the newly discovered pathogen Severe Fever with Thrombocytopenia Syndrome (STFS) virus, and placed it in the Bunyaviridae family, along with the hantaviruses and Rift Valley Fever virus. Later investigation has placed its mortality rate at 12 percent.

Yu, a specialist in tick-borne bacteria like the species responsible for HGA, first suspected that a virus might be responsible for the outbreaks after close examination of patients’ clinical data showed big differences from symptoms produced by HGA, and blood sera drawn from patients revealed no HGA or HGA antibodies.

Yu became certain that a virus was at fault after sera taken from patients retained its ability to kill cells, despite being passed through a filter that blocked all bacteria. Still, initial genetic tests failed to generate a match with a known pathogen.

“Clearly, we had a virus, but what virus?” Yu said. “I told the people I was working with that they needed to be even more careful, because we were working with an unknown.”

That caution seemed appropriate when electron microscope studies of deactivated virus particles revealed what appeared to be a hantavirus — associated in Asia with hemorrhagic fever and in the Americas with a deadly pulmonary syndrome. But when Yu and his colleagues managed to extract the virus’ entire genetic code, they found that it didn’t match any other known virus.

When researchers from the Chinese Center for Disease Control and Prevention led by study author Dr. Yu Wang analyzed sera taken from 241 symptomatic patients from Henan, Hubei, Shandong, Anhui, Jiangsu and Liaoning provinces, they found 171 contained either the previously unknown virus itself or antibodies against it. In addition, the scientists found the virus in 10 out of 186 ticks collected from farm animals in the area where the patients lived.

“This seems to be a tick-borne disease, and the disease comes out when the ticks come out, from late March to late July,” Yu said. “Fortunately, even though the full life cycle is not clear, we know that for the virus humans are a dead end — we don’t have human-to-human transmission as we did with SARS.”

STFS

Shown in red are areas where SFTS surveillance was carried out and SFTS bunyavirus was isolated from patients (Source: NEJM).

The China Mega-Project for Infectious Diseases, the Western Regional Center of Excellence for Biodefense and Emerging Infectious Diseases and the Chinese Recruitment Program of Global Experts provided support for this research.

The article can be found at: Yu XJ et al. (2011) Fever with Thrombocytopenia Associated with a Novel Bunyavirus in China.

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Source: New England Journal Of Medicine.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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