China Battles Bird Flu With Spray And Mass Slaughters [PHOTOS]

REUTERS/StringerAn employee wearing a protection suit sprays disinfectant on chickens at a poultry market in Hefei, Anhui province April 5, 2013.A seventh person died in on Sunday from a new strain of deadly bird flu, the H7N9 virus, that has infected at least 24 people in eastern China.

That means about thirty percent of those with severe infections die, which is relatively high, Yanzhong Huang, director of global health studies at Seton Hall University, told Bloomberg News on Monday.

See China's response to the new bird flu strain >

The strain currently only spreads from bird to human.

The key worry now is that H7N9 could mutate and begin spreading from human to human, though no cases have been reported yet.

There's is a concern, however, that milder cases of bird flu have been going undetected.

Laurie Garrett, senior editor for the Council on Foreign Relations, pointed out on Twitter that even patients who are seriously ill test "weakly positive." That means people could have the virus, but not know it until they begin showing violent flu-like symptoms. By then, it can be too late.

Additionally, China expert Victor Shih also said that patients are deterred from getting treated because of the outrageous hospital fees.