Health officials in east China's Jiangxi Province on Saturday confirmed a second human case of the virus strain. A 55-year-old woman is now in critical condition.
She first showed symptoms of a sore throat and dizziness in early January, and was admitted to hospital last Wednesday. The patient reportedly once visited an agricultural market.
People who have had close contact with the patient so far haven't shown any abnormal symptoms of their own.
The first human case of the H10N8 virus was reported in a 73-year-old female patient in the same province last month. She later died from respiratory failure.