How to Quarantine a New Horse: Lessons from Washington's Flu Case

How to quarantine a new horse: the short version

Here's how to quarantine a new horse: keep it physically apart from your other horses for about two weeks, with its own equipment, and check its temperature twice a day. Vets commonly recommend 14 to 21 days, and longer if the horse came from a high-risk setting like an auction, so confirm the exact length with your own vet.

The AAEP's owner handout says new horses should be quarantined for two weeks. Its quarantine checklist adds three core rules:

• No nose-to-nose contact with other horses.
• Dedicated equipment for the new horse, and minimal use of shared facilities.
• Chores last. Take care of the new horse after everyone else.

The EDCC suggests at least 7 to 14 days for horses from low-risk barns, and longer when the risk is higher. Colorado State University Extension gives a range of 7 to 30 days. An auction horse with an unknown history sits at the high end of that scale.

What happened in Washington

On October 20, 2026, The Horse published an EDCC Health Watch report: one horse in Pierce County, Washington, tested positive for equine influenza. According to the Assistant State Veterinarian, the horse had been purchased at an auction and is under veterinary care. The Equine Disease Communication Center (EDCC) listing is dated October 19.

The EDCC alert, sourced to the Assistant State Veterinarian at the Washington State Department of Agriculture (WSDA), lists one confirmed horse at a private facility under voluntary quarantine and says the horse is recovering. It gives the number of exposed horses as unknown, so it's too early to say whether other horses were affected.

One case isn't an outbreak. Still, it's a textbook example of the risk every buyer takes in fall, when sales, shows and clinics move a lot of horses between barns. Flu spreads through coughs, sneezes, shared buckets and contaminated hands, clothing and tack, so a new arrival can carry it home before anyone sees a symptom.

Set up the isolation area

The goal is to stop direct contact, shared air and shared objects. You don't need a fancy barn, just a plan you can stick to for a few weeks.

Space and airspace

• Best: a separate paddock or stall well away from the main barn. CSU Extension suggests 35 to 200 meters (about 115 to 650 feet) from other horses and downwind of the main barn.
• Good enough: an end stall with an empty stall between the new horse and the residents.
• Avoid: a shared fence line, a shared water trough or a stall across the aisle. Some diseases can travel about 300 feet in the air, according to the AAEP.

If your new horse is anxious alone, a companion it can see from a distance helps. Contact over the fence defeats the purpose. For horses that panic when separated, our guide to the buddy sour horse has calming ideas.

Gear that stays with the new horse

Label or color-code everything and keep it in the isolation area:

• Water and feed buckets, hay net
• Halter and lead rope
• Brushes, hoof pick and fly mask
• Blanket, saddle pad and any tack you use
• Its own thermometer
• Pitchfork, muck bucket and wheelbarrow, if you can manage it

Never dip a shared hose into the new horse's bucket. The AAEP warns against putting a hose into your bucket at shows, and the same logic applies at home: a hose can carry germs from bucket to bucket.

Daily routine during quarantine

A simple routine is easier to follow than a perfect one you abandon in week two.

Order of chores

1. Feed, water and clean stalls for your resident horses first.
2. Do the new horse last.
3. Wash your hands, or use gloves, before going back to other horses.
4. If you can, wear a separate jacket or coveralls and boots for the isolation area. A shallow footbath at the entrance helps.
5. In a boarding barn, ask whether one person can handle the new horse exclusively.

Temperature checks twice a day

The thermometer is your simplest daily check. With equine influenza, the AAEP says a dry, harsh cough usually comes before the fever, but not every infected horse coughs. Log temperatures and listen for a cough.

• Take a rectal temperature morning and evening and write it down. CSU Extension recommends a first reading within a few hours of arrival.
• Normal for an adult horse is roughly 99 to 101.5°F (37.2 to 38.6°C). Evening readings tend to run a little higher.
• The AAEP treats anything over 101.5°F (38.6°C) as a concern. CSU suggests rechecking within an hour if a reading lands between 101 and 102°F.

If you've never taken a horse's temperature, our first aid kit and vital signs guide walks through it. Our health basics page covers what's normal.

Signs that mean calling the vet

Call your vet the same day if the new horse shows any of these:

• A temperature above 101.5°F, especially if it stays up on a recheck
• Coughing, particularly a dry, hacking cough
• Nasal discharge, watery or thick
• Swelling under the jaw or throatlatch
• Going off feed, dullness or weakness
• Stumbling, weakness in the hind end or any neurologic signs
• Diarrhea

Equine influenza can cause a high fever of up to 106°F, a dry cough, watery nasal discharge and a dull, off-feed horse, The Horse notes. Strangles and EHV-1 can look similar early on, so don't guess. Your vet may want to test before the horse ever leaves isolation.

For disease details, read our guides to equine influenza, strangles and EHV-1.

Before you buy: questions for the seller

Good biosecurity starts before the horse loads. Auctions mix horses from many barns, often with unknown histories, which makes them higher risk than buying from a private barn you can visit.

Ask the seller, or the sale company, for:

• Vaccination records, with dates and products, including influenza
• A current negative Coggins (EIA test); see what a Coggins test is
• A health certificate (CVI) if the horse is crossing state lines. CSU suggests asking for one issued within 14 days
• Any recent coughing, fever, nasal discharge or illness in the barn
• Where the horse has been in the last month, including shows, sales or transport

If the records are missing, assume the horse isn't vaccinated and plan a longer isolation with your vet. A pre-purchase exam is a good moment to talk through both vaccines and quarantine.

Returning horses count too

Quarantine isn't only for strangers. The AAEP recommends isolating your own horses after a trail ride or show based on how risky the trip was.

A solo state-park ride is low risk. A big multi-state show that doesn't require vaccines or a negative Coggins is high risk. US Equestrian requires proof of an equine influenza vaccine within the previous six months for its sanctioned competitions, The Horse notes, but local shows and sales outside its rules may not require it.

If you're hauling to events this fall, our show prep section and long-distance hauling guide cover the trip itself.

What to do and what to watch next

• This week: If you bought a horse at a fall sale, start the isolation routine now, even if it looks healthy.
• Before you buy: Get vaccination records and a Coggins in writing, and book your vet for an arrival check.
• Daily: Log temperatures twice a day and do the new horse last.
• Talk to your vet about whether your herd's flu vaccines are current going into winter.
• Watch the EDCC alerts for new cases in your area. We'll update this article if Washington officials report further cases linked to this one.

New to owning horses? Our care guide and get started pages are good next reads.