China, where the coronavirus originated, could see a second wave of the virus, as new cases appear in the northeastern part of the country. Zhong Nanshan, the Chinese government's senior medical adviser, told CNN Saturday that most Chinese are still “susceptible” to the virus.

"The majority of ... Chinese at the moment are still susceptible of the Covid-19 infection, because (of) a lack of immunity," Zhong said. "We are facing (a) big challenge, it's not better than the foreign countries I think at the moment."

At the beginning of the outbreak, Zhong said local authorities in Chinese cities such as Wuhan were not transparent about the total number of cases. The virus is believed to have originated at an animal and seafood market in Wuhan.

"The local authorities, they didn't like to tell the truth at that time," Zhong said. "At the very beginning they kept silent, and then I said probably we have (a larger) number of people being infected."

Ben Cowling, a professor at the School of Public Health at the University of Hong Kong, told CNBC in mid-April that China may have already been in a second wave.

U.S. intelligence has claimed in a report that China has concealed the extent of the country’s coronavirus outbreak. Chinese Foreign Ministry spokeswoman Hua Chunying has hit back at the allegations, claiming Beijing has been “open and transparent” in its response to the virus and accusing Washington of shifting the blame for its handling of the pandemic.

In recent weeks, China has seen at least new cases in Jilin, a northeastern province on the border of North Korea and Russia. Jilin City has gone into partial lockdown to contain an outbreak of at least 21 cases, shutting down public transportation and banning social gatherings.

“The current outbreak is very serious and complex and poses a major risk of further spread,” Gai Dongping, vice-mayor of Jilin, told reporters Wednesday. “In order to prevent and stem the spread of the epidemic, the Jilin epidemic prevention and control group has decided to implement control measures in the urban area of Jilin.”

China’s National Health Commission said Sunday that five new coronavirus cases were detected on Saturday in mainland China, down from eight the previous day. As of Sunday at 12:40 p.m. ET, there are 84,047 coronavirus cases and 4,638 deaths.