states. the first case was detected in n o. patieas fully vaccinated, but not boosted, and had recently traveled to south africa. hundreds of cases of the new variant have now been confirmed in more than 20 countries, prompting the biden administration to prepare stricter testing requirements for all travelers entering the united states, including americans. today, president biden said this is why boosters are needed, and implored americans to get that additional dose. 135 million americans are eligible for boosters. only about 42 million have actually gotten them so far pb cbs anna werner leads off our coverage tonight from san francisco. good evening, anna. reporter: good evening, margaret. as you said, cbs news has learned the first known u.s. omicron patient came through here, san francisco international airport. now, public health officials are crediting the state s large-scale testing program for finding that case. they say testing will now be stepped up at airports.