Influenza A virus: sampling of the unique shorebird habitat at Delaware Bay, USA

Delaware (DE) Bay, in the northeastern USA, has long been recognized as a hotspot for avian influenza A virus (IAV); every spring, this coastal region serves as a brief stopover site for thousands of long-distance migrating shorebirds, en route to breeding grounds in the Arctic. During these stopovers, IAV has been consistently recovered from ruddy turnstones (Arenaria interpres) that are likely to become infected as they feed by probing sand and cobble in search of food. In May 2010–2012, we successfully isolated 19 IAV from environmental samples (sand, n = 18; horseshoe crab eggs, n = 1) obtained from DE Bay sites. Two of these viruses were subjected to laboratory conditions similar to those in the DE Bay spring-time environment, and remained infectious for 7 days. Here, through the recovery of IAV from environmental samples, temperature monitoring at and below the sand surface and simulated laboratory trials, we provide evidence that the beach environment may enable localized transmission and short-term maintenance of IAV in this unique ecosystem.