By Steven Grattan (Reuters) -The Pan American Health Organization (PAHO) on Wednesday warned of the growing number of COVID-19 cases caused by the highly infectious BA.4 and BA.5 Omicron subvariants of the coronavirus even as overall cases dipped in the Americas. There were 1,562,967 new COVID-19 cases in the Americas last week, a 0.9% decrease, PAHO said at a news conference, while deaths fell 3.5% to 4,789. But PAHO Director Dr. Carissa Etienne cautioned that the Omicron subvariants, now dominant in the United States and several other countries, “is driving new infections across the Americas…