The Trump administration formally notified the United Nations of its withdrawal from the World Health Organization, although the pullout won't take effect until next year, meaning it could be rescinded under a new administration or if circumstances change. Former Vice President Joe Biden, the presumptive Democratic presidential nominee, said he would reverse the decision on his first day in office if elected.

The withdrawal notification makes good on President Donald Trump's vow in late May to terminate U.S. participation in the WHO, which he has harshly criticized for its response to the coronavirus pandemic and accused of bowing to Chinese influence. The move was immediately assailed by health officials and critics of the administration, including numerous Democrats who said it would cost the U.S. influence in the global arena.

Harvard University and the Massachusetts Institute of Technology filed a federal lawsuit challenging the Trump administration's decision to bar international students from staying in the U.S. if they take classes entirely online this fall. The lawsuit, filed in Boston's federal court, seeks to prevent federal immigration authorities from enforcing the rule. The universities contend that the directive violates the Administrative Procedures Act because officials failed to offer a reasonable basis justifying the policy and because the public was not given notice to comment on it.

U.S. Immigration and Customs Enforcement notified colleges Monday that international students will be forced to leave the U.S. or transfer to another college if their schools operate entirely online this fall. New visas will not be issued to students at those schools, and others at universities offering a mix of online and in-person classes will be barred from taking all of their classes online.

At least 58 people died in several days of flooding in Japan, in the wake of pounding rain that caused deadly floods in the country's south, before moving north battering large areas of the main island, swelling more rivers, triggering mudslides and destroying houses and roads. Parts of Nagano and Gifu, including areas known for scenic mountain trails and hot springs, were flooded by massive downpours.

Public broadcaster NHK showed a swollen river gouging into its embankment and destroying a highway. In the city of Gero, the rising river was flowing just below a bridge. Most of the dead were from hardest-hit Kumamoto prefecture. Four others died in Fukuoka, another prefecture on Kyushu, Japan's third-largest island. At the peak, as many as 3.6 million people were advised to evacuate, although it wasn't mandatory and the number who sought shelter was not known.

A major research effort is under way to understand whether Covid-19 can spread through tiny airborne particles that are released by infected people and remain suspended in the air for hours. Scientists are working alongside sanitary engineers at the World Health Organization to investigate how tiny aerosols bearing the virus may be released into the environment; whether they are spread around rooms by air-conditioning units; and how infectious the particles may be.

Among the studies being conducted are experiments with caged hamsters to assess whether viruses wafting through the air in hospitals and other high-risk settings are sufficiently potent to spread infections. In an open letter published this week, the scientists implied that the WHO was underplaying the risk of airborne transmission, prompting the organisation to concede that the possibility could not be ruled out.