EDWARDS AIR FORCE BASE, Calif -- A 10-man team from the Air Force Flight Test Center traveled to Riverside to help fight an epidemic of Newcastle disease that was decimating the California poultry industry. The U.S. Department of Agriculture had made an emergency request for military personnel to augment US Department of Agriculture personnel to inoculate healthy flocks of chickens and turkeys and destroy diseased ones. Additional teams of enlisted personnel, officer coordinators and base veterinarians rotated in and out of the afflicted counties until 14 August to help contain the epidemic.
Influenza viruses are part of the Orthomyxoviridae family and are negative sense single-stranded RNA viruses with segmented genomes. There are four main influenza virus species: A, B, C and D. Type A viruses are known to infect a wide variety of birds and mammals, while the other species have more restricted host ranges. Influenza A viruses (IAV), including all avian influenza viruses, possess eight separate genomic segments ranging in size between 890 and 2341 nucleotides Like other RNA viruses, influenza viruses have a fast mutation rate, typically accumulating two to eight substitutions per 1000 sites per year. Segmentation further increases the evolutionary speed of the virus by permitting exchange of genes between virus strains that co-infect cells in the same host, a process known as reassortment. The genome segments of IAV encode ten core polypeptides, including: three subunits of a viral polymerase, a nucleoprotein, three transmembrane proteins (haemagglutinin (HA), neuraminidase (NA) and the M2 ion channel), a matrix protein M1 and ‘non-structural’ proteins NS1 and NS2/NEP, as well as a virus strain-dependent suite of non-essential accessory proteins. The HA and NA surface proteins are antigenic, very diverse, encoded on separate segments and split into 18 and 11 subtypes, respectively. Apart from the recently discovered bat-specific H17, H18, N10 and N11 proteins [5,6], all of the subtypes have been found in avian species, whereas only a subset of the others have been detected in mammals. The other six segments are often considered as encoding the ‘internal’ genes. Although there is continuous global circulation of IAV in humans, due to the connectivity of the population [7], the majority of the diversity is in avian species and the reservoir population is avian. Therefore, understanding the general global patterns of IAV epidemiology in birds will help elucidate the origins of past pandemics and could help inform predictions about future events.