(Reuters) - Here’s what you need to know about the coronavirus right now: Trump faces backlash for removing mask U.S. President Donald Trump faced a backlash on Tuesday for removing his mask when he returned to the White House and urging Americans not to fear COVID-19. In a made-for-television spectacle, Trump descended from his Marine One helicopter wearing a white surgical mask only to remove it as he posed, saluting and waving, on the mansion’s South Portico. “Don’t let it dominate you. Don’t be afraid of it,” Trump said in a video after his return from the Walter Reed Medical Center military hospital. Vice President Mike Pence and challenger Kamala Harris will be separated by a plexiglass barrier during their debate on Wednesday in an effort to lower the risk of coronavirus transmission, the commission overseeing the event said. CDC revises guidance U.S. Centers for Disease Control and Prevention (CDC) on Monday said COVID-19 can spread through virus lingering in the air, sometimes for hours, acknowledging concerns widely voiced by public health experts about airborne transmission. The CDC guidance comes weeks after the agency published – and then took down – a similar warning, sparking debate over how the virus spreads. In Monday’s guidance, CDC said there was evidence that people with COVID-19 possibly infected others who were more than 6 feet away, within enclosed spaces with poor ventilation. Under such circumstances, CDC said scientists believe the amount of infectious smaller droplet and particles, or aerosols, produced by people with COVID-19 become concentrated enough to spread the virus. World’s highest rate of positive cases Argentina has the world’s highest rate of positive COVID-19 tests, according to Oxford-linked tracker Our World In Data, with nearly six out of 10 yielding an infection, a reflection of low testing levels and loose enforcement of lockdown rules. Argentina hit 809,728 confirmed cases on Monday, with a 7-day rolling average of around 12,500 new daily infections. The country passed 20,000 fatalities last week. Medical professionals said low-levels of testing and lax restrictions had propelled the high positive rate. China in talks with WHO on vaccines for global use China is in talks to have its locally-produced COVID-19 vaccines assessed by the World Health Organization, as a step toward making them available for international use, a WHO official said on Tuesday. Hundreds of thousands of essential workers and other groups considered at high risk in China have been given locally-developed vaccines even as clinical trials had not been fully completed, raising safety concerns among experts. Socorro Escalate, WHO’s coordinator for essential medicines and health technologies in the Western Pacific region, said China had held preliminary discussions with WHO to have its vaccines included in a list for emergency use. Self-isolating Commission head snubs EU advice The head of the European Commission, Ursula von der Leyen, said she would leave quarantine on Tuesday after having been in contact with someone positive for COVID-19 a week earlier, despite EU recommendations of 14 days of self-isolation. Von der Leyen, 61, is following Belgium’s rules, which have just been softened, but her decision to ignore the stricter advice from the bloc’s public health body could further weaken calls for an EU common approach to battle the epidemic.