A woman in southern China was diagnosed with the H5N6 Avian Influenza virus and is in critical condition, Xinhua reported Wednesday. The flu was first reported in humans last May in southwestern China and, so far, four cases have been reported around the world, according to the state-run news agency.

Chinese officials reportedly said the case was an isolated one, much like the four reported before it, and authorities expect little risk of the flu spreading. The 26-year-old woman is admitted in a local hospital in the region, Xinhua reported, citing the Guangdong health department. 

Earlier cases of H5N6 virus showed the patients to have been exposed to “live poultry or potentially contaminated environments, especially markets where live birds have been sold,” the World Health Organization (WHO) reported. The male patient diagnosed with H5N6 last May died from the virus. The condition of the other patients infected with the virus is not yet known.

Another case of H5N6 was reported in China in February, when a 44-year-old man from Yunan province was diagnosed with the virus and was admitted in a hospital. WHO issued a warning at the time while announcing the diagnosis, and said travelers "should avoid poultry farms, or contact with animals in live bird markets, or entering areas where poultry may be slaughtered, or contact with any surfaces that appear to be contaminated with faeces from poultry or other animals." However, the organization did not advise any screening at points of entry then. 

According to the Centers for Disease Control and Prevention, symptoms of a highly pathogenic Avian Influenza A Virus infection include shortness of breath, difficulty in breathing, pneumonia, acute respiratory distress, viral pneumonia and respiratory failure. The symptoms are sometimes accompanied by nausea, abdominal pain, diarrhea, vomiting, or an altered mental status or seizures. According to WHO, the virus does not transmit easily between humans.

Last year, the United Nations expressed alarm over the H5N6 virus, which causes a high death rate in chicken and geese.

"Influenza viruses are constantly mixing and recombining to form new threats," Juan Lubroth, chief veterinary officer at the U.N.'s Food and Agriculture Organization, reportedly said, adding: "However, H5N6 is particularly worrisome, since it has been detected in several places so far from one another and because it is so highly pathogenic, meaning infected poultry quickly become sick and, within 72 hours, death rates are very high."