MEXICO CITY (Reuters) - The new variant of the coronavirus first detected in Britain has been confirmed in northern Mexico, health officials said on Sunday, adding a new layer of concern to an already severe national outbreak. The confirmation of the especially contagious new variant of the virus marks the first time it has been found in Mexico, home to the pandemic’s forth-highest death toll globally. A 56-year-old British man who flew on Dec. 29 from Mexico City to the city of Matamoros, just south of the U.S.-Mexico border, tested positive for the new strain, both state and national health officials said on Sunday. The man arrived to the Mexican capital a day earlier on a flight from Amsterdam, said Jose Luis Alomia, the head of epidemiology for the national health ministry, at a regular government news conference. The official explained that upon arriving in Matamoros, the man did not show any symptoms of COVID-19, the disease caused by the virus. But he nonetheless tested positive again after a second test was administered to him on Dec. 31. Alomia stressed that while the new variant has been detected, it is not believed to be circulating on any significant scale among the population. A dozen passengers on the same Mexico City-Matamoros flight have not yet been identified, officials said, while the rest of the 45-passenger flight have all tested negative, including the plane’s crew. The British man remains hospitalized in Matamoros, and was placed on a ventilator on Saturday. Officials did not say that any form of contact tracing or testing had been conducted on passengers on the Amsterdam-Mexico City flight. The fast-spreading new strain of the virus has also been found in South Africa and Australia, prompting authorities to take more aggressive action to prevent even greater contagion as countries across the globe struggle to contain the pandemic.