What Is Orf Virus?

Medically Reviewed by Jabeen Begum, MD on October 13, 2022
4 min read

What is orf virus?

Orf virus in humans is a common and widespread zoonotic viral infection that affects the skin. It is caused by the parapoxvirus and appears worldwide. Orf virus has many names: contagious pustular dermatitis, ecthyma contagiosum, sore mouth infection, and sheep pox in humans. 

While this disease is primarily found in goats and sheep, where it causes lesions to develop around their mouth, it can also be transmitted to humans, sometimes by deer or cattle. Transmission occurs when humans with an open sore come into direct contact with an infected animal. 

The main difference between animal and human orf virus infections is that humans develop lesions on their hands instead of around or inside their mouths.

Those most at risk of infection include farmers and other people who live around livestock, especially sheep and goats. A few activities put you at even greater risk for becoming infected, including: 

  • Tending to sheep or goats by bottle feeding, tube feeding, or sheering them 
  • Engaging in casual contact with infected animals, such as petting 
  • Coming into contact with contaminated equipment 
  • Being bitten by an animal with orf virus 

While it’s easy for orf to spread from an animal to a human, it’s rare for this infection to be passed from person to person. 

Orf virus causes lesions to develop, primarily on the forearms, hands, and fingers. In rare cases, lesions can occur on the face as well. These lesions can be painful and can remain on your skin for two months. However, most lesions heal in a few weeks. The lesions usually appear anywhere from three to seven days after contact with an infected animal, and when they heal, they typically don’t leave scars. 

Orf lesions are generally few in number and are around two to three centimeters in diameter. Some may grow as large as five centimeters, though. A lesion may be tender in its early stages. Additionally, you may experience enlarged lymph nodes on your elbow or underneath your arm, along with red streaks. A mild fever may develop, and you may also feel fatigued.

Orf Virus Appearance

When infected, humans may first notice a pimple appear on their affected skin. The pimple eventually develops into a lesion. This lesion typically has a red center with a white ring around it. As the lesion grows, it turns red and begins seeping pus. Temporary hair loss may result from the lesion if it is located around hair follicles. 

As it progresses, the lesion will dry out, and you’ll notice tiny black spots forming on the surface. Finally, the lesion becomes flat, and a dry crust forms around it. At this point, the healing process begins.

Orf Virus Complications 

Though they are rare, complications can occur. You’re at a greater risk of complications if you’re immunocompromised due to conditions like HIV or chemotherapy treatments. Complications may include bacterial infection, a rash that looks like a bulls-eye target, or a skin condition known as bullous pemphigoid, which forms large blisters.

It’s important to see your doctor if you suspect you have contracted orf. Some infectious diseases that are passed between livestock and humans may be mistaken for orf but will come with more serious complications that must be treated. For example, anthrax can be mistaken for orf and then prove fatal. For this reason, it’s important that a proper diagnosis is received. 

A viral swab, electron microscopy, or a skin biopsy can confirm if orf is present. 

Orf is self-limiting, which means that your body typically heals on its own without medical intervention. As of now, no medical treatments have been widely approved for treating orf, though you can treat your infection with supportive, at-home care, managing the lesions until they’re fully healed. 

Since bacteria can cause lesions to become infected, you must keep each lesion covered and dry. In some cases, such as those involving manual labor, the lesion may become wet instead, so it’s essential to cover it with a waterproof bandage. The sore can be uncovered during periods of rest or at bedtime (though you should make sure your sheets are clean to prevent infection), and this helps encourage healing. 

Local antiseptics may be used along with moist bandages or dressings. If the lesion becomes infected with a secondary bacterial infection, an antibiotic will need to be prescribed.

For individuals who develop a severe fever, severe pain, or lesions that grow or spread rapidly, consultation with your doctor should be considered. 

Orf vaccinations are available for sheep and goats, but a person can still contract the virus by coming into contact with a recently vaccinated animal. There is no vaccination to protect humans from getting orf, though there are some preventive measures that you can take to decrease your chances of becoming infected, including: 

  • Protecting your hands when around sheep and goats, typically by wearing latex gloves 
  • Covering any open sores with waterproof bandaging 
  • Frequently washing your hands with soap and warm water, especially after touching animals 
  • Regularly cleaning and disinfecting barns, sheds, and other livestock kennels 
  • Vaccinating your sheep and goats 

Additionally, humans may develop some immunity to the orf virus after their initial infection, though subsequent infections can still occur. However, any following orf infections may present less severe symptoms.