A recent report to the OIE indicates that the dog in China that initially tested as a “weak positive” for the COVID-19 virus last week (February 26th) was positive again on retesting on February 28th. That’s more suggestive of the dog being truly infected, versus a positive from transient contamination from the infected owner.
Here is the summary from the report (to clarify, the virus that causes COVID-19 was recently named SARS-CoV-2. So COVID-19 is the name of the disease/illness, but SARS-CoV-2 is the name of the bug):
The dog was placed under quarantine on 26 February 2020 after its owner was hospitalised due to COVID-19 infection. Following veterinary examination nasal, oral, rectal swabs as well as faeces were taken after the dog’s admission to the quarantine facility. Nasal and oral samples tested positive for SARS-CoV-2. The dog has not exhibited any specific clinical signs. Additional samples taken on 28 February also tested positive. Investigations are continuing to determine the duration of virus detection. Risk management measures are in place for this case, including cleansing and disinfection of the premises, and proper personal hygiene and protection. Mammalian pets from households with confirmed human cases of COVID-19 will be be placed under quarantine and veterinary surveillance for 14 days. Samples will be collected for testing of SARS-CoV-2 as appropriate.