What's the data to inform us how this infection spread so quickly? It seems that the virus first appeared in around November 2019 in China and an infected person visited the seafood market in Huanan, Wuhan where it is likely the virus mutated in that environment becoming far more virulent. So, maybe we are looking at one person, a super spreader, or more than one person getting infected when the virus was amplified by the animals there, or several viruses combined in the animals to form the SARS-Cov-2 virus infection those persons.

But the virus rapidly spread to other countries without animal reservoirs amplifying it. How did that happen?

1 Answer 1


Phylogenetic analyses of the virus in the community has shown that the virus has been introduced at multiple times by different persons because clades inside one city differ from clades in different cities in the same country.

By analysing 48 almost complete virus genome sequences, we found out that the viruses that invaded Taiwan, the United States, and Japan were introduced independently. We identified thirteen parsimony-informative sites and three groups (CTC, TCC, and TCT). None of the viruses found in cities in Taiwan, the United States, and Japan formed a monophyletic clade with viruses found in other cities in the same country. These results suggest the difficulty of implementing effective border measures against this virus.

Genome phylogenetic tree analyses revealed evidence that the severe acute respiratory syndrome coronavirus 2 had been introduced to Taiwan, the United States, and Japan several times Tomoko Matsuda1 and Norichika Ogata1,2,*1 Nihon BioData Corporation, Kawasaki, Japan, 2 Medicale Meccanica Inc., Kawasaki, Japan

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