Sample collection
Under the permission and supervision of the Shanghai wildlife protection
and management office, a total of 6,944 throat and anal swab samples of
wild birds were collected in the Nanhui Dongtan wetland of Pudong
(30°51′ to 31°06′ N, 121°50′ to 121°51′ E) and Jiuduansha Natural
Reservation Zone (31°06′ to 31°14′ N, 121°46′ to 122°15′ E), Shanghai,
China from 2016 to 2019. All wild birds were released after the samples
were collected. The swabs were placed in a 5 ml cryopreserved tubes
containing 2 ml virus carrier fluid and stored at -80℃ refrigerator for
further analysis.