(Released 19 January 2016) On January 15, 2016, the United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) reported detection of highly pathogenic avian influenza (HPAI) H7N8 virus in a commercial turkey flock in Dubois County, Indiana. Subsequently, APHIS reported detection of low pathogenic avian influenza (LPAI) H7N8 among 8 nearby turkey flocks*. There are nine known subtypes of avian influenza H7 viruses (H7N1, H7N2, H7N3, H7N4, H7N5, H7N6, H7N7, H7N8, and H7N9); most of these have been LPAI viruses. LPAI H7N8 virus has been detected previously in wild bird surveillance in the United States, but this is the first instance of HPAI H7N8 virus detection in poultry.
Avian influenza viruses are ified as either low pathogenic or highly pathogenic depending upon molecular characteristics of the virus and the virus’ ability to cause disease and mortality in chickens in a laboratory setting. Infection of poultry with LPAI viruses may cause no disease or mild illness (such as ruffled feathers and a drop in egg production) and may not be detected. Infection of poultry with HPAI viruses can cause severe disease with high mortality in birds. Both HPAI and LPAI viruses can spread rapidly through poultry flocks. Influenza viruses are constantly changing and LPAI H7 viruses have been known to rapidly evolve into HPAI viruses.
CDC Risk Assessment
Human infection with avian influenza viruses is rare, but can occur. Human infections with avian influenza viruses have most often occurred after unprotected close contact with infected birds or the excretions/secretions of infected birds (e.g., droppings, oral fluids). Infected birds shed virus in their saliva, mucous and feces. Human infections with avian influenza viruses can happen when enough virus gets into a person’s eyes, nose or mouth, or is inhaled. This can happen when virus is in the air (in droplets or possibly dust) and a person breathes it in, or when a person touches something that has virus on it then touches their mouth, eyes or nose. Human infection with avian influenza viruses has not occurred from eating properly cooked poultry or poultry products.
At this time no human infections with avian influenza H7N8 viruses have ever been reported worldwide, however other avian influenza H7 viruses have infected people sporadically, including both LPAI and HPAI H7 viruses. H7 virus infections in people have been associated with a wide range of illness from conjunctivitis only, to influenza-like illness, to severe respiratory illness.
At this time, CDC considers the risk to the general public from these H7 viruses to be low; however, because other avian influenza A H7 viruses have infected people, it is possible that human infections with these viruses could occur. Risk is dependent on exposure. People with close or prolonged unprotected contact with infected birds or contaminated environments are likely to be at greater risk of infection. It is important to note that this is an evolving situation with some uncertainty. The public health risk assessment and associated recommendations may change.
CDC recommends the same protective measures for HPAI H7N8 outbreaks in birds as was recommended for domestic HPAI H5 outbreaks that occurred during late 2014 and 2015.This is consistent with guidance for exposure to novel influenza viruses with the potential to cause severe disease in humans. Anyone with exposure to infected birds or potentially-contaminated environments should be monitored for certain signs and symptoms of illness for 10 days after their last possible exposure, even if exposure to the sick birds was minimal or if personal protective equipment (PPE) was worn appropriately. Most of the signs and symptoms of avian influenza infections in humans overlap with those of other respiratory illnesses (like seasonal influenza). CDC has developed fact sheets for avian influenza outbreak responders and people who own or work with poultry experiencing AI outbreaks. There is no recommendation that exposed persons with no symptoms of illness limit routine activities or contact with others during the 10-day monitoring period. People with exposure who develop symptoms compatible with avian influenza infection should limit routine activities and contact with others as much as possible until testing to determine the cause of their illness is completed.
Guidance for clinicians and public health professionals in the United States on appropriate follow-up, specimen collection, processing, testing and treatment is available at http://www.cdc.gov/flu/avianflu/healthprofessionals.htm. CDC currently recommends the influenza antiviral drugs oseltamivir, peramivir, or zanamivir for treatment of human infection with avian influenza viruses. Clinicians should prescribe antiviral medications for treatment of people who become ill with specific symptoms and who had exposure to avian influenza without waiting for test results.
The Indiana State Department of Health is implementing their HPAI public health monitoring plan (which includes monitoring of both avian influenza responders and other persons exposed to birds infected with HPAI and LPAI viruses) to facilitate timelyentification of possible human infections with these viruses, prompt medical evaluation and treatment if needed, and reducing the opportunities for ongoing spread.
USDA/APHIS is implementing the HPAI Preparedness and Response Plan[509 KB, 19 pages] published in September 2015.
*A 10th farm with suspect but unconfirmed LPAI H7N8 also is being depopulated.
Indiana State Department of Health, Epidemiology Resource Center Ph: 317-233-7125
Signs and symptoms to watch out for include: fever (temperature of 100ºF [37.8ºC] or greater) or feeling feverish, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, eye redness (or conjunctivitis) difficulty breathing. Also possible are diarrhea, nausea, vomiting, fatigue, seizures or rash.
More information about avian influenza can be found at http://www.cdc.gov/flu/avianflu/index.htm.