Since 2013, more than 1,200 people in China have been infected with the H7N9 bird virus.
Of these lab-confirmed cases, more than a third were diagnosed after October 2016. China is currently in the midst of its fifth avian flu epidemic, one that’s already deadlier than any of the preceding outbreaks. Forty-one percent of the 460 confirmed cases have resulted in death, according to a CDC report.
As of now, the World Health Organization has said that the risk of the virus spreading from human-to-human, and thus the likelihood of the epidemic developing into a pandemic, is low (the vast majority of cases in China were believed to be contracted directly from an infected bird).
But experts are on the lookout for mutations that could allow the virus to spread more easily between people.
“Constant change is the nature of all influenza viruses,” Wenqing Zhang, head of the WHO’s global influenza program, said on Wednesday. “This makes influenza a persistent and significant threat to public health.”
Per the Washington Post, the virus has already separated into two different branches. While the US maintains a stockpile of H7N9 vaccines, they are designed to treat the older lineage of the disease.
The CDC is working to help develop a vaccine that will specifically target the new strain of the virus, but according to the Post, testing and producing such a vaccine will take a few months.