One of the points I endeavored to make a few weeks ago in Because A Pandemic Doesn't Happen In A Vacuum, is that just because we are currently overwhelmed by COVID-19 and its economic impacts, the world won't stop serving up new challenges.
We are entering the peak months of our spring severe weather season, are less than two months from the start of the Atlantic Hurricane Season, earthquakes can occur at anytime, and there is nothing to say we couldn't be blindsided by yet another public health crisis in the months ahead.While avian flu has been fairly subdued around the world for the past couple of years, and almost absent in the United States, today the USDA and APHIS are reporting the discovery of an HPAI H7N3 virus at a turkey farm in South Carolina.
This is the first reported HPAI outbreak in the United States since 2017 (see USDA Identifies Tennessee Bird Flu Virus as HPAI H7N9), and appears to be the result of an LPAI-to-HPAI mutation (see graphic at top of blog). This this can happen when a relatively harmless low path H5 or H7 virus is allowed to circulate in poultry.
North American H7 viruses are unlikely to produce the sort of human health concerns that the Asian H7N9 virus did in China, but we've seen a few mild human infections with that subtype in the past (see MMWR: Mild H7N3 Infections In Two Poultry Workers - Jalisco, Mexico).For now, this outbreak appears to only impact one turkey farm, and the human health risk is low. The affected poultry have been depopulated, and we will watch for any signs of spread to nearby farms, or via migratory birds, in the days ahead.
USDA Confirms Highly Pathogenic H7N3 Avian Influenza in a Commercial Flock in Chesterfield County, South Carolina
USDA Animal and Plant Health Inspection Service sent this bulletin at 04/09/2020 04:05 PM EDT
April 9, 2020, Washington, D.C. – The United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed the presence of highly pathogenic H7N3 avian influenza (HPAI) in a commercial turkey flock in Chesterfield County, South Carolina.
This is the first confirmed case of HPAI in commercial poultry in the United States since 2017. It appears this HPAI strain mutated from a low pathogenic strain that has been found in poultry in that area recently.
No human cases of this H7N3 avian influenza virus have been detected and there is no immediate public health concern. As a reminder, the proper handling and cooking of poultry and eggs to an internal temperature of 165 ˚F kills bacteria and viruses.
Samples from the affected flock, which experienced increased mortality, were tested at the Clemson Veterinary Diagnostic Center, part of the National Animal Laboratory Network, and confirmed at the APHIS National Veterinary Services Laboratories (NVSL) in Ames, Iowa. Virus isolation is ongoing. APHIS is working closely with the South Carolina State Veterinarian’s Office, part of Clemson University, on a joint incident response. State officials quarantined the affected premises, and birds on the property were depopulated to prevent the spread of the disease. Birds from the flock will not enter the food system. As part of existing avian influenza response plans, Federal and State partners are working jointly on additional surveillance and testing in the nearby area.
The United States has the strongest AI surveillance program in the world, and USDA is working with its partners to actively look for the disease in commercial poultry operations, live bird markets and in migratory wild bird populations. USDA will report this finding to the World Organisation for Animal Health (OIE) as well as international trading partners. USDA also continues to communicate with trading partners to encourage adherence to OIE standards and minimize trade impacts. OIE trade guidelines call on countries to base trade restrictions on sound science and, whenever possible, limit restrictions to those animals and animal products within a defined region that pose a risk of spreading disease of concern.
All bird owners, whether commercial producers or backyard enthusiasts, should continue to practice good biosecurity, prevent contact between their birds and wild birds, and report sick birds or unusual bird deaths to State/Federal officials, either through their state veterinarian or through USDA’s toll-free number at 1-866-536-7593. Additional information on biosecurity for can be found at
Additional background Avian influenza (AI) is caused by an influenza type A virus which can infect poultry (such as chickens, turkeys, pheasants, quail, domestic ducks, geese and guinea fowl) and is carried by free flying waterfowl such as ducks, geese and shorebirds. AI viruses are classified by a combination of two groups of proteins: hemagglutinin or “H” proteins, of which there are 16 (H1–H16), and neuraminidase or “N” proteins, of which there are 9 (N1–N9). Many different combinations of “H” and “N” proteins are possible. Each combination is considered a different subtype, and can be further broken down into different strains. AI viruses are further classified by their pathogenicity (low or high) — the ability of a particular virus strain to produce disease in domestic poultry.