Pelosi arrives in Taiwan;New study on Masks;US kills al-Qaeda leader;Most compelling primary races

A Japanese scholar's research found that masks could be an overlooked source of infection. The researchers found several pathogenic microbes on the three types of masks including gauze masks, polyurethane masks, and non-woven masks.

Joe Biden announced that al-Qaeda leader Ayman al-Zawahiri was killed in a U.S. drone strike in Afghanistan last weekend. It was the biggest blow to al-Qaeda since the group's founder Osama bin Laden was killed in 2011.

Five states - Arizona, Kansas, Michigan, Missouri and Washington - will hold primaries today, on Aug. 2. Eleven of these races are seen as the latest test of President Trump's influence.