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Ohio State University Extension


African Swine Fever: A Severe Threat to Swine Herds Is on the United States’ Doorstep

Veterinary Preventive Medicine
Scott P. Kenney, PhD, Assistant Professor, Ohio Agricultural Research and Development Center, Ohio State University Extension, Wooster

African swine fever is a disease caused by the African swine fever virus (ASFV). ASFV is a viral pathogen found primarily in sub-Saharan Africa. Recently, it has spread through China, Mongolia, Vietnam, parts of Europe and has been detected in the western hemisphere for the first time in over 40 years in the Dominican Republic and Haiti. It has never been found in the United States but remains a constant threat. The virus does not infect people but is devastating to domestic and wild pigs and kills up to 100% of infected animals. No vaccine is approved for use against ASFV in the United States.Two domestic pigs standing next to each other.

Symptoms of Illness

People working with pigs should look for signs of ASFV. The sooner these signs are recognized and reported, the faster the industry can respond and stop the spread of the disease. Signs include high fever; decreased appetite; weakness; red, blotchy skin or skin lesions; diarrhea and vomiting; coughing; and difficulty breathing.

There are four main types of disease depending on the strain of virus infecting the pigs:

  • peracute
  • acute
  • subacute
  • chronic

In the peracute form, pigs die within four days post-infection without clinical signs (90–100% of the pigs will die from this form).

The acute form kills within four to 21 days post-infection, usually with animals showing the symptoms listed above.

The subacute form is caused by less deadly isolates, resulting in 30–70% of the pigs dying after 20 days post-infection.

Chronic disease is noted in ASFV infection with low virulent isolates, causing delayed growth, emaciation, joint swelling, skin ulcers, and lesions associated with secondary bacterial infections (Sanchez-Cordon, Montoya, Reis, and Dixon 2018).

Immediately report animals with any of these signs to state or federal animal health officials by calling the Ohio Department of Agriculture animal disease hotline at (800) 300-9755 or (614) 728-6220; or by calling the U.S. Department of Agriculture (USDA) toll-free number, 1-866-536-7593, for testing and investigation. Speedy recognition of symptoms and subsequent testing is essential to prevent the spread of ASFV.

Public Health Consequences

Humans are not infected by ASFV, and it cannot be transmitted to people via food (not a foodborne disease). Losses of at least 10–30% or more of the United States’ swine population are anticipated, based on outbreaks in other countries (Woonwong, Tien, and Thanawongnuwech 2020). This would increase pork prices, limit exports, and result in other negative impacts.

Risk Factors

Factors that increase the risk for ASFV infection include the presence of free-range pigs in surrounding areas, proximity to infected farms, and swill feeding in backyard farms. Excessive numbers of farm visitors, especially those who have traveled to areas that may have ASFV, should be avoided.

How to Prevent Infection

The risk of importing the virus from other countries is high because this virus is harder to kill and more infectious than other pig viruses. For this reason, do not bring back pork or pork products from any foreign country. If you have visited farms while abroad or participated in any swine-related activities, such as boar hunting, declare those activities as international farm visits to U.S. Customs and Border Protection when you return. Also, thoroughly clean and disinfect, or dispose of, any clothing or shoes worn around pigs—including feral pigs and wild boars—before returning to the United States. Impose a self-quarantine, do not visit farms, state fairs, livestock markets, sale barns, zoos, circuses, pet stores with pot-bellied pigs, or any other animal facility with pigs for at least five days after you return.

Good biosecurity practices are critical to preventing ASFV and other viral pathogens from rapidly spreading. Swine owners should have a Secure Pork Supply (SPS) plan. Check out how to create a plan at An SPS plan is essential to assuring continuity of business in case of an outbreak, even if your animals are not infected. The Ohio State University College of Veterinary Medicine is working on a project to assist Ohio pig farmers in developing SPS plans at no cost. If you are interested in learning more, contact Dr. Andreia Arruda at

More details regarding ASFV can be found on the USDA Animal and Plant Health Inspection Service website at

Information and tips for swine showers at county fairs are on the Ohio 4-H youth development website at hemorrhages from African swine fever on a pig’s chest, throat, and jaw.


Sanchez-Cordon, P.J., M. Montoya, A L Reis, and L K Dixon. 2018. “African Swine Fever: A Re-emerging Viral Disease Threatening the Global Pig Industry.” Veterinary Journal, Volume 233, March 2018: 41–48.

Woonwong, Yonlayong, Duy Do Tien, and Roongroje Thanawongnuwech. 2020. “The Future of the Pig Industry After the Introduction of African Swine Fever Into Asia.” Animal Frontiers, Volume 10, Issue 4, October 2020: 30–37.

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Originally posted Feb 18, 2022.