Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 7/3/2013
Publication Date: 9/17/2013
Citation: Swayne, D.E., Pantin Jackwood, M.J., Spackman, E., Kapczynski, D.R., Suarez, D.L., Hamilton, K. 2013. Understanding the 2013 H7N9 avian influenza outbreak in poultry: field epidemiology and experimental pathogenesis studies [abstract]. Abstracts for Influenza 2013: One Influenza, One World and One Health, Oxford, United Kingdom, September 17-19,2013. CDROM. Interpretive Summary:
Technical Abstract: The influenza A (H7N9) virus is of avian origin and is responsible for infections in human in large urban areas of China in spring 2013. The original source of the virus from poultry farms is unknown but the live poultry market (LPM) system has served as an amplifier of the virus, especially in wholesale markets in the large cities, with 77% of human cases having known contact with live poultry at a retail live poultry markets. There has been no new human infection in large urban areas where LPM system has been closed. There have been no known human cases on farms or among veterinarians. The virus is low pathogenic based on intravenous pathogenicity index test in chickens. Furthermore, intranasal inoculation of chickens, domestic ducks, domestic geese, Japanese quail and pigeons with a human H7N9 influenza isolate resulted in infection, but no clinical signs. A few deaths of chickens do occur if high inoculum doses (8log10) are given. Virus shedding in quail and chickens was much higher and more prolonged than in ducks and geese, and pigeons were most difficult to infect. In limited transmission studies, quail effectively transmitted the virus to direct contacts, and pigeons and ducks did not. The virus was detected at much higher levels from oropharyngeal than cloacal swabs, and surveillance sampling should preferentially target this sampling type. The high viral shedding from chickens and quail create a likely source of infection for humans. Virus shedding patterns in ducks (with the exception of the Muscovy ducks) and geese were shorter and of lower titer than gallinaceous poultry. Pigeons were difficult to infect unless given high doses of inoculum intranasally and are unlikely to be involved in field spread.