At least four people in China have been infected with a new strain of bird flu, known as H7N9— and two of the people who have contracted the disease have died, according to the World Health Organization.
The cases were confirmed to be the new strain of bird flu late last week by the China CDC—two of the cases were found in Shanghai and one in the Anhui province. A fourth case was confirmed by the state-run CCTV news channel Tuesday. That case occurred in Nanjing, in eastern China.
According to WHO, sufferers experienced a "respiratory tract infection with progression to severe pneumonia and breathing difficulties. Two of the four victims have died, with a third in critical condition.
WHO says it is "following the event closely" but it has not been able to identify where the disease was contracted and whether or not the virus is transmissible between humans. According to local news reports, some of the victims worked closely with poultry.
Researchers have become increasingly worried about bird flu after researchers showed last year that the H5N1 bird flu virus could be easily modified to be transmissible between humans. Joseph Kim, a researcher developing a "universal" flu vaccine that would be effective against all strains of the virus, says that a global flu pandemic is "inevitable" once a strain of the virus develops that can be passed between humans.