A toll booth operator wearing a mask hands some change to a driver at the Houshayu toll station in Shunyi district, Beijing, on Monday. The city’s first H7N9 case was reported on Saturday after a 7-year-old girl in the district was confirmed to have been infected with the new strain of avian influenza. Photo: Li Hao/GT

Security guards stand on duty on Monday to register vehicles and people entering Gucheng village in Shunyi district, Beijing, where the city’s first confirmed bird flu case was reported on Saturday. Photo: Li Hao/GT

A security guard disinfects a rug at the entrance to Gucheng village in Shunyi district, Beijing, where the city’s first confirmed bird flu case was reported on Saturday. Photo: Li Hao/GT

Security guards wearing masks on duty in their car on Monday, where they were preventing people approaching the home of a four-year-old H7N9 flu virus carrier surnamed Zhu in Naidong village, Chaoyang district, Beijing. Photo: Li Hao/GT

Two local residents wearing masks pass by the home of a four-year-old H7N9 flu virus carrier surnamed Zhu in Naidong village, Chaoyang district, Beijing, on Monday. Photo: Li Hao/GT

A mother and her child, with their masks on, pass by the home of a four-year-old H7N9 flu virus carrier surnamed Zhu in Naidong village, Chaoyang district, Beijing, on Monday. Photo: Li Hao/GT

A poster, illustrating how to prevent infections of the H7N9 virus, stuck to a wall in Naidong village of Chaoyang district, Beijing, on Monday. Photo: Li Hao/GT

Staff members from the Naidong village committee, in Beijing’s Chaoyang district, disinfect areas of the village on Monday. The municipal health authorities announced on Monday a four-year-old boy surnamed Zhu from the village was an H7N9 flu virus carrier. Photo: Li Hao/GT

Security guards wearing masks check whether a van is carrying live poultry at the entrance to Naidong village, in Chaoyang district, Beijing, on Monday. The municipal health authorities announced on Monday a four-year-old boy surnamed Zhu from the village was an H7N9 flu virus carrier. Photo: Li Hao/GT