Washington, July 14 (TIWN) America's top infectious diseases expert Anthony Fauci has said the US was witnessing the new surge in the number of COVID-19 cases was because the country never shut down entirely.

"We did not shut down entirely," Xinhua news agency quoted Fauci, director of the US National Institute of Allergy and Infectious Diseases, as saying during a webinar with the Stanford School of Medicine on Monday.

"We need to draw back a few yards and say, 'OK, we can't stay shut down forever'... You've got to shut down but then you've got to gradually open," he said.

Fauci said the US has not "even begun to see the end" of the coronavirus pandemic yet as scientists continue to work on potential drugs and vaccines for the virus, according to the report.

The top infectious diseases expert said he is "cautiously optimistic" scientists will be able to create at least one safe and effective vaccine by the end of the year or early 2021.