America's top infectious diseases expert has warned the United States is facing a "serious problem" from a resurgent coronavirus as the illness puts the brakes on reopening two of the country's largest states.

India now has more than 500,000 confirmed coronavirus cases, according to government figures released Saturday that showed a record daily leap of 18,500 new infections.

While China moved closer to containing a fresh outbreak in Beijing, the coronavirus took a stronger hold elsewhere, including the United States, where surging infections across southern states have highlighted the risks of reopening economies without effective treatment or vaccines.

Another record daily increase in India on Friday pushed the country's caseload toward half a million, and other countries with large populations like Indonesia, Pakistan and Mexico grappled with large caseloads and strained health care systems.

Health workers fanned out across suburbs of Melbourne Friday in a testing blitz aimed at choking off a surge in coronavirus cases in Australia's second-biggest city.

The White House said Thursday President Donald Trump will travel to New Jersey this weekend as planned even though it is one of three states recommending that people who have been to coronavirus hot spots self-quarantine for two weeks.

A new scientific study by Italy's national health institute ISS shows that mosquitoes are unable to transmit coronavirus to humans, the institute said Thursday.

Between five and eight percent of the total U.S. population has experienced infection with the new coronavirus, a top health body said Thursday as it warned pregnant women were at higher risk of getting severe COVID-19.

Europe has seen a surge of COVID-19 cases since countries began easing restrictions aimed at curbing the spread of the potentially fatal virus, the World Health Organization said Thursday.

Iran on Thursday announced 134 new deaths from the novel coronavirus took the overall toll in the Middle East's deadliest outbreak past 10,000.

Governments and businesses are ramping up precautions as coronavirus case numbers rise to dire new levels in parts of the U.S. and around the world, potentially wiping out two months of progress.