The statistician said found the rate of the coronavirus spreading “very worrying” because people appear not to know they are infecting others.
He told MailOnline: “I find it very worrying both medically because the infection seems to have a relatively long incubation period and therefore people are infective for a longer time before they realise they may have the disease, and financially because China is so important to the world economy.”
Dr Ghebreyesus confirmed the delay in detection of the disease was worrisome.
He said: “My biggest worry is that there are countries today who do not have the systems in place to detect people who have contracted with the virus, even if it were to emerge.
“Urgent support is needed to bolster weak health systems to detect, diagnose and care for people with the virus, to prevent further human to human transmission and protect health workers.”