The World Health Organization defines zoonosis as any infection naturally transmissible from vertebrate animals to humans. Coronaviruses are zoonotic, meaning they are transmitted between animals and people. Detailed investigations found that SARS-CoV was transmitted from civet cats to humans and MERS-CoV from dromedary camels to humans. Several known coronaviruses are circulating in animals that have not yet infected humans.

The most likely ecological reservoirs for SARS-CoV-2 are bats, but it is believed that the Virus jumped the species barrier (spillover) to humans from another intermediate animal host. This intermediate animal host could be a domestic food animal, a wild animal, or a domesticated wild animal that has not yet been identified. Thus, COVID-19 should be classified as an "emerging infectious disease (EID) of probable animal origin."

More than 232,672,955 40 million human COVID-19 infections reported appear to be exclusively through human-human transmission. Although the initial one hundred COVID-19 patients were presumably exposed to the Virus at a seafood market in China, 33 of 585 swab samples collected from surfaces and cages in the market tested positive for SARS-CoV-2, no virus was isolated directly from animals, and no animal reservoir was detected.

It has also been reported that patients may continue to remain positive of the Virus even after symptoms have stopped for up to 8 days [51,52]. Thus, clinicians and policy makers should painstakingly check COVID-19 infected individuals before being discharged. Otherwise, these asymptomatic carrier individuals who interact closely with community members may continue to serve as main reservoir for infection transmission and inadvertently infect others