BRASILIA, Oct 27 (Reuters) - COVID-19 is slowly retreating across most of North, Central and South America, the Pan American Health Organization (PAHO) said on Wednesday, reporting that last week the continent"s death and infection figures were the lowest in over a year. Many of the larger Caribbean islands are seeing downward trends, including Cuba, the site of a major months-long COVID-19 outbreak.However, Paraguay saw a doubling of coronavirus cases in the last week and Belize a sharp jump in COVID-related deaths, the regional branch of the World Health Organization said in a briefing. "We have reason to be optimistic, but we must remain vigilant," PAHO Assistant Director Jarbas Barbosa said.He urged authorities to continue to implement public health measures like mask-wearing, social distancing and limiting large gatherings, especially as many countries are still struggling to expand vaccine coverage. Nearly 44% of people in Latin America and the Caribbean have completed their COVID-19 immunizations, thanks largely to donations, made bilaterally or through the WHO-led COVAX facility. Over 3 million more doses will arrive in the region through COVAX this week, as deliveries pick up in the final months of the year, Barbosa said. He appealed to leaders of the G20 major economies meeting this weekend in Rome to do more to hasten equitable distribution of vaccines through donations, saying no country would be safe while others were still unprotected against the coronavirus. Barbosa said health was taking center stage at the COP26 climate summit that starts on Sunday in Glasgow. Around the world, more than 12 million deaths every year are associated with environmental risk factors, including high temperatures, air pollution, wildfires and droughts, according to PAHO. "Left unaddressed, climate change would transform our environment, our food systems and living conditions, with potentially devastating consequences for our health," he said.