Beginning Jan. 5, all travellers to the U.S. from China will be required to take a COVID-19 test no more than two days before travel and provide a negative test before boarding their flight.Concerns over possibility of new variantsIn a statement explaining the testing, the U.S. Centers for Disease Control and Prevention (CDC) cited the surge in infections and what it said was a lack of adequate and transparent information from China, including genomic sequencing on the viral strains circulating in the country.But the CDC's action may be less about stopping a new variant from crossing U.S. borders and more about increasing pressure on China to share more information, said Dr. David Dowdy, an infectious disease epidemiologist at Johns Hopkins Bloomberg School of Public Health, adding he hopes the restrictions "aren't kept in place longer than they need to be."Early warning programDr. Stuart Campbell Ray, an infectious disease expert at Johns Hopkins University, agreed China isn't sharing enough genomic sequencing information.Japan, India among those requiring testingIn an abrupt change of policy, China this month began dismantling the world's strictest COVID-19 regime of lockdowns and extensive testing, putting its battered economy on course for a complete reopening next year."