The United States now has the highest number of confirmed cases of the coronavirus, overtaking China, where the pandemic started last December.

There were 83,507 cases in the United States by the end of Thursday, according to Johns Hopkins University’s coronavirus tracker, nearly 2,000 more than China’s. Fatalities remain much higher in Italy, Spain and china.

Experts and public health officials have said cases will continue to grow in the United States, unlike in China, because of aggressive testing, a trend that has been seen in New York state, which leads all US states in reported cases and fatalities.

The World Health Organization has said the United States could potentially turn into the next epicenter of the pandemic based on the continued increase in the number of new cases, the highest currently for any one country as a proportion of the world tally.

There were 529,000 confirmed coronavirus cases worldwide by the end of Thursday, according to the Johns Hopkins tracker, and 23,956 fatalities.