EHV-1 in Horses: Respiratory vs Neurologic Signs and Show Biosecurity

On Sept. 24, 2026, the Equine Disease Communication Center (EDCC) posted a Maryland Department of Agriculture report of EHV-1 respiratory disease in Baltimore County, a newly confirmed case of EHV-1 in horses. The horse is a 4-year-old sport horse mare used for showing, kept at a private facility. The Equiery ran the same alert that day.

Here's what's confirmed so far:

• Signs began: Sept. 20, 2026
• Confirmed: Sept. 22, 2026
• Status: alive
• Vaccination status: not reported
• Form: respiratory, not neurologic

This is one confirmed case. Still, it lands in the busiest stretch of the fall show calendar, so it's a good week to brush up on EHV-1 in horses and tighten your barn habits.

What is EHV-1 in horses?

EHV-1 in horses is equine herpesvirus type 1, a very common virus that most horses meet early in life. Usually it causes a mild respiratory illness, but in a small share of horses it can also cause abortion in pregnant mares, illness in newborn foals or a serious neurologic disease called EHM.

Like other herpesviruses, EHV-1 can hide. A horse that caught it years ago may carry the virus silently and start shedding it again when stressed, for example by hauling, a show or a change of barn. The 2024 ACVIM consensus statement cites recent studies estimating that 15% to 27% of horses carry the virus in this hidden form.

That is why a healthy-looking horse can bring EHV-1 home from a show. It's also why good habits matter at every event, not only when there's news.

Respiratory vs neurologic EHV-1 (EHM)

The same virus can look very different from horse to horse.

According to the AAEP, EHV-1 often causes a two-phase fever: one spike around day 1 or 2 after infection and a second around day 6 or 7. Respiratory cases usually don't cough much.

Signs of EHM, the neurologic form

With EHM there may be few respiratory signs, so fever above 101.5°F (38.6°C) is often the only warning. The AAEP lists these neurologic signs:

• Stumbling or poor coordination, especially behind
• Hind limb weakness or swaying
• Loss of tail tone (the tail feels limp when you lift it)
• Dribbling urine
• Dullness or lethargy
• Head tilt
• Leaning on a wall or fence for balance
• Being unable to get up

The ACVIM consensus notes that most EHM clusters happen in late autumn, winter and spring, and lists older age and being female as risk factors.

How EHV-1 spreads

EHV-1 spreads mainly through nasal secretions. The AAEP lists these routes:

• Nose-to-nose contact over stall walls, at the in-gate or on the trailer
• Shared water and feed buckets
• Tack, grooming tools and wipe rags used on more than one horse
• People's hands and clothes, the route most often forgotten
• Trailers that carried a shedding horse
• The air near a horse that is shedding the virus

The virus usually survives up to about 7 days in the environment, and up to a month in ideal conditions. The good news: most disinfectants kill it easily, as long as you clean off dirt and manure first.

Incubation is typically 4 to 6 days, but it can be as short as 24 hours. A horse can come home from a weekend show looking perfect and run a fever midweek.

Why fall show and travel season matters

Fall packs a lot of risk into a few weeks: championship shows, clinics, sales, and long hauls between states. Horses from many barns share aisles, wash racks and water sources, and travel stress can reactivate hidden virus in carrier horses.

The AAEP says the classic way EHV-1 spreads is horses coming home from events, even events where no disease was reported. Check your show's health rules and entry requirements before you go; our Coggins test guide covers the paperwork side.

Horse show biosecurity checklist

Print this, tape it in the tack room and share it with your barn. For more packing ideas, see show prep.

Before you leave

• Take and record every horse's temperature for a few days so you know their normal
• Talk to your vet about whether your horse's vaccines are current for your plans
• Pack your own buckets, hay net, sponges, towels and a digital thermometer
• Don't travel a horse that has a fever or nasal discharge

At the show

• No nose-to-nose greetings with other horses, including friends' horses
• Never use communal water troughs; fill your own bucket from the hose without dunking the nozzle
• Don't share bits, sponges, rags or grooming tools
• Wash or sanitize your hands between your horse and anyone else's
• Take temperatures twice a day, morning and evening, and write them down

When you get home

• Isolate returning horses and new arrivals away from the herd, with their own buckets, tools and turnout
• Keep taking temperatures twice a day; the AAEP suggests at least 21 days of separation, and your vet can tailor that
• Handle and feed the isolated horses last, or wear separate boots and outer clothes
• Clean, then disinfect, trailers, buckets and tack
• Wash show clothes in hot water with detergent

What vaccination does and doesn't do

Vaccines for EHV-1 exist, and many vets recommend them for show and breeding horses. According to the AAEP, some can reduce nasal shedding and help protect against respiratory disease and abortion.

What they don't do: no current vaccine carries a label claim for preventing EHM, and the ACVIM consensus found no evidence that vaccination prevents it. A vaccinated horse can still get infected, so vaccinate as part of the plan, not as the whole plan.

Your vet will pick the product and schedule for your horse's age, job, travel and whether a mare is pregnant.

When to call the vet right away

Call your veterinarian immediately, and don't move horses on or off the property, if you see:

• A temperature above 101.5°F (38.6°C), especially after a show or a new arrival
• Wobbliness, stumbling or a weak, swaying hind end
• Dribbling urine or trouble urinating
• A limp tail or a horse leaning on the wall
• Nasal discharge with fever in a horse that recently traveled
• A pregnant mare that has been exposed or runs a fever

EHV-1 can only be confirmed with lab tests your vet runs, such as a nasal swab and a blood sample. Don't guess from signs alone, and let the vet decide on care. Keep a thermometer in your kit; our first aid kit checklist shows how to take vital signs.

What to watch next

• The EDCC alert board. Check equinediseasecc.org/alerts weekly this fall for new cases near you. One confirmed case is not a cluster, and updates will say if anything changes.
• Your show's announcements. Organizers and state animal health officials post any new entry rules.
• Other fall diseases. Maryland also reported a fatal West Nile case in Cecil County the same day; see our West Nile virus guide. Strangles has also been reported at boarding barns this month, so read our strangles explainer.

The habit that protects against all of these is the same: a thermometer, a notebook and a no-sharing rule. For more everyday basics, visit health basics.