MEXICO CITY (AP) — As many as one-third of Mexicans may have been exposed to the coronavirus by the end of 2020, according to a study of random blood samples taken between February and December. Antibodies were found in 33.5% of samples from blood banks and medical laboratory tests in Mexico unrelated to COVID-19. The levels varied according to regions; the highest exposure rate was in the northwest at 40.7%, and the lowest was in western states, at 26.6%. In general, areas along the U.S. border had higher rates. The rate may have risen by as much as ten percent on average nationwide following the upsurge in cases in January.