BRASILIA, Dec 1 (Reuters) - The new Omicron variant of the coronavirus is likely to soon spread to other countries in North and South America after being detected in Canada and Brazil, the Pan American Health Organization (PAHO) said on Wednesday. World Health Organization (WHO) officials said 24 countries have reported cases of the variant, prompting many nations to tighten their borders. read more "It is not yet clear whether Omicron is more transmissible than other variants, or if it causes more severe disease," said PAHO Director Carissa Etienne, adding that it will take time to test the variant. "Speed and transparency are especially critical at this time. But above all, we urge people not to be frightened." Until the neutralization tests and other laboratory assays are completed, experts will not have enough evidence to determine the degree of transmissibility or severity of the Omicron variant, or to assess the effectiveness of the COVID-19 vaccines against it, Etienne told reporters on a webcast news conference. Over the last week in North America, COVID-19 cases in Canada and the United States remained steady but high, while infections and deaths have dropped by over 20% in Mexico, the regional health agency said. In Central America, every country except Panama has seen a reduction infections and deaths, PAHO reported. In South America, cases in Southern Cone countries have increased steadily for the past several weeks, while in the Andean region and in Brazil, infections are plateauing. Omicron was designated a "variant of concern" by the World Health Organization on Friday. read more