Historically, the Yukon-Kuskokwim (Y-K) Delta has had high rates of the respiratory virus RSV in infants and young children. It’s been the highest in the United States, and the second-highest in the world, according to Brian Lefferts, the director of public health for the Yukon-Kuskokwim Health Corporation (YKHC). He said that while RSV isn’t usually serious for adults, it can be devastating for young children.