A father and son in Beijing, March 22. Photo: Nicolas Asfouri/AFP via Getty Images

Classified Chinese government data suggests that one-third of coronavirus cases in the country were asymptomatic "silent carriers," according to the South China Morning Post, the English-language paper in Hong Kong.

Why it matters: Because of the high number of asymptomatic cases, China and South Korea started testing people who had close contact with a patient — regardless of whether they had flu-like symptoms.

  • This testing standard may explain how the two Asian countries have slowed the spread of the virus. Hong Kong is testing airport arrivals in the city, even if travelers have no symptoms.

By the numbers: "More than 43,000 people in China had tested positive without immediate symptoms by the end of February and were quarantined," SCMP reports.

The big picture: The number of infections is rapidly rising in most European countries and the United States, where for the most part only those with symptoms are being tested.

Go deeper: Even the best coronavirus scenario is terrible

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Bryan Walsh, author of Future
1 hour ago - Science

The murder hornets are here

A braver man than me holds a speciment of the Asian giant hornet. Photo: Karen Ducey/Getty Images

Entomologists in Washington state on Thursday discovered the first Asian giant hornet nest in the U.S.

Why it matters: You may know this insect species by its nom de guerre: "the murder hornet." While the threat they pose to humans has been overstated, the invading hornets could decimate local honeybee populations if they establish themselves.

Biden is highest-spending political candidate on TV ads

Joe Biden. Photo: Sean Rayford/Getty Images

After spending an additional $45.2 million on political ads this week, former Vice President Joe Biden has become the highest-spending political candidate on TV ads ever, according to data from Advertising Analytics.

By the numbers: In total, the Biden campaign has spent $582.7 million on TV ads between 2019 and 2020, officially surpassing Michael Bloomberg's record spend of roughly $582 million. Biden's spend includes his primary and general election advertising.