Hong Kong is seeking a meeting with Shenzhen officials after a second H7N9 case from across the border, though authorities there claim otherwise.
The sufferer is an 80-year-old man who lives in Fu Yong Xin He in Shenzhen's Bao An district.
He was admitted to a hospital near his home on November 13 for management of a chronic illness and left the facility on November 29.
He arrived in Hong Kong on Tuesday with family members and took a taxi from the Shenzhen Bay control point in the afternoon to the Accident and Emergency Department of Tuen Mun Hospital.
He developed fever on Friday morning and was isolated. He tested positive for bird flu H7N9 later that day and was transferred to Princess Margaret Hospital where he remains in a stable condition.
And the condition of a 36-year-old Indonesian domestic helper, the first H7N9 case in Hong Kong, has improved from critical to serious at Queen Mary Hospital. She had fallen ill after buying a live chicken in Shenzhen.
Secretary for Food and Health Ko Wing-man said yesterday: "The Centre for Health Protection is maintaining a very close liaison with mainland authorities, particularly Shenzhen.
"It has been agreed in principle that within a few days the CHP will send experts to the mainland to have meetings with their mainland counterparts to strengthen collaboration."
Still, Shenzhen authorities have insisted they have no human or poultry cases of H7N9.
Meanwhile, 19 close contacts of the elderly man are under a 10-day quarantine. They all tested negative for H7N9 but are on a course of Tamiflu.
Among the 19 are five members of the man's family and the taxi driver who took him from Shenzhen Bay Port Border Control Point to Tuen Mun Hospital last Tuesday.
There are also 13 patients who were in the same area as the elderly man at Tuen Mun Hospital. One of them had developed a fever but then tested negative for H7N9.
Seven of the close contacts have been put under quarantine at the Lady MacLehose Holiday Village in Sai Kung and another 140 contacts are being monitored.
In the case of the Indonesian helper, 11 of 17 close contacts have completed quarantine, though they will stay under medical watch for 10 more days.
The remaining six close contacts remain under quarantine.