Dr. Michael Ryan(L), executive director of the World Health Organization (WHO) Health Emergencies Program, addresses a press conference in Geneva, Switzerland, Feb. 18, 2020. (Photo by Chen Junxia/Xinhua)

Wuhan is not necessarily the place where the COVID-19 disease crossed from animals into humans, said a senior WHO expert.

GENEVA, Aug. 3  -- Although the first clusters of atypical pneumonia were reported in Wuhan, China, it doesn't necessarily mean that is where the COVID-19 disease crossed from animals into humans, a senior World Health Organization (WHO) expert said on Monday.

Dr. Michael Ryan, executive director of the WHO Health Emergencies Program, said at a routine COVID-19 briefing on Monday that a much more "extensive retrospective epidemiological study" should be taken to fully understand the links between the cases.