Bird flu is on the rise in China, and that has the Center for Disease Control concerned that a global pandemic could follow.
"Among the viruses we've assessed... H7N9 is the most concerning" Dr. Tim Uyeki, a medical epidemiologist in CDC's influenza division, said to Vox.
"We don't know when the next pandemic is going to start, where it's going to start," Uykei continued, "but at this time the biggest concern is the H7N9 virus."
China has confirmed 460 cases of the H7N9 bird flu virus since last October, the most of any season since the first human case was reported in 2013.
H7N9 isn't a new virus â it's sickened people in China for four years, and about a third of people infected die from the virus.
But experts say the virus has changed its lineage. It appears H7N9 is no longer responding to oseltamivir (Tamiflu), andÂ has possibly mutated into a highly pathogenic, or more contagious to humans, disease.
Health officials are worried that, in the case of a global pandemic, the changes in the virus will render the 12 million emergency doses of the vaccine in the U.S. less effective.
"America has long been unprepared for a dangerous pandemic, but the risks are especially high under President Trump," former Ebola response coordinator Ron Klain told Vox.
Trump has yet to name aÂ new head to the Centers of Disease Control and Prevention, the agency that would lead a pandemic response.
Bird flu viruses, including H7N9, originate in aquatic bird species and are eventually transmitted to domestic poultry flocks. The virus lingers and is passed to other birds and flocks at open-air poultry markets.
Poultry workers are at the highest risk of contracting the virus, which causes pneumonia in humans and a range of other reactions. So far, the virus has only spread to humans through contact with poultry.
Last week, Tennessee officials confirmed a case of H7N9 there, thoughÂ it is genetically different from the virus in China andÂ less likely to be transmitted through human-to-human contact.
No other cases of the H7N9 have been reported outside China or Vietnam.
- The raging bird flu in China is a good reminder the US isn't prepared for a pandemic (Vox)
- Human cases of bird flu are surging, alarming public health officials (Stat)
- Tennessee bird flu shares name, not genetics, of feared China strain (Reuters)