GENEVA, Feb. 29 (Xinhua) -- The World Health Organization (WHO) on Friday raised the global risk level of COVID-19 from high to very high due to two reasons, its chief said on Saturday.

The global risk level has been raised because of, first, the "difficulty in identifying cases due to non-specific symptoms and the potential of undetected transmission," and second, the "potential for major impact on healthcare systems in some affected and potentially affected countries," WHO Director-General Dr. Tedros Adhanom Ghebreyesus said on Twitter.

He also cited the "spread of the new coronavirus and countries' capacity to respond" as the basis for raising the risk level and said WHO risk assessments have been shared with public health authorities, including through the International Health Regulations Event Information Site.

"The assessments are undertaken and updated regularly to inform decision-making and planning," he said, adding that the risk within China remains unchanged as "very high."

"WHO is currently working closely with partner agencies for human/animal health," said Tedros. "We're waiting for further results from Hong Kong as health officials investigate the reported presence of COVID-19 in one pet dog."

According to reports, a dog in Hong Kong has tested positive for COVID-19, but local scientists are not sure if the dog was actually infected or if it picked up the virus from a contaminated surface.

"Past experience with coronaviruses and our current understanding of COVID-19 do not indicate that common household pets spread the disease or make people sick. We will provide further updates as we learn more," the WHO chief said.