The husband of a Canadian who was diagnosed earlier this week with bird flu after returning from a trip to China has also tested positive for the virus, health officials said Friday.

The couple in their 50s began feeling sick days after returning home in westernmost British Columbia province.

Tests confirmed the first human case of H7N9 bird flu in North America in the woman on Monday. Her husband's diagnosis was confirmed three days later.

"Since both cases became symptomatic one day apart, it is likely they were exposed to a common source, rather than one having been infected by the other," said Canada's chief public health officer, Gregory Taylor.

Neither patient required hospitalization and both are recovering in self-isolation at home from their illness, said officials.

During an outbreak in China two years ago there were fears it could mutate to become easily transmissible between people, threatening a global pandemic.

But Chinese officials and the World Health Organization have said there is no evidence of sustained human-to-human transmission, despite occasional instances of apparent infection between family members.

Since March 2013, China has recorded 281 deaths and 470 cases of H7N9.