2.2 Sample collection
A total of 3160 swab samples were collected between September to
December of 2019 in 14 provinces of China (including Hubei), mainly for
routine surveillance on avian diseases, such as avian influenza viruses
(AIV), Newcastle disease viruses (NDV), etc. The swab samples were
collected through taking smears at both cloacal and oropharyngeal tracts
of a bird, and stored in 1.5 mL phosphate buffered saline (PBS, pH 7.2)
containing 10% glycerol. The RNA was extracted using an RNeasy Mini Kit
(Qiagen, Hilden, Germany) following manufacturer’s instructions, and
stored at -80°C.