Are Worms in Humans Contagious?

Some worms in humans are contagious and some are not. Pinworm spreads easily from person to person, usually within a household, while roundworm, whipworm and hookworm do not pass directly between people, because their eggs or larvae need time in contaminated soil before they can infect anyone.

This page explains, worm by worm, how each one is caught, whether it can pass to the people around you, whether pets play a part, and the everyday habits the CDC recommends to stop the spread. It is general education, not medical advice.

Which worms spread from person to person?

The short answer for the worms people most often ask about:

• Pinworm: yes. It is the most contagious worm infection in the United States and often affects several people in one home.
• Roundworm (Ascaris): not directly. Eggs passed in stool have to mature in soil before they can infect someone.
• Whipworm: not directly. Like roundworm, its eggs become infective only after time in soil.
• Hookworm: not directly. Its larvae develop in soil and get in through bare skin, most often the feet.
• Strongyloides: rarely. It is usually caught from soil, but the CDC describes rare person-to-person spread in places such as long-term care facilities and daycare centers, and through organ transplants.
• River blindness (onchocerciasis): no. It is spread by the bites of infected blackflies, not by contact with another person.

The sections below explain each one. For an overview of the signs and tests for each worm, see our guide to intestinal worms in adults.

Pinworm: the contagious one

The CDC calls pinworm the most common worm infection in the United States, and says it spreads easily in households, childcare centers and other group settings. It is most common in school-aged and preschool-aged children, in people living in institutions, and in the household members and caretakers of someone who has it.

How pinworm spreads

While an infected person sleeps, female pinworms leave the intestine and lay eggs on the skin around the anus. The CDC says the eggs can infect another person within two to three hours, and that they spread in three main ways:

• From hands to mouth. Eggs get onto fingers or under fingernails after scratching or touching the area, and then reach the mouth.
• From objects. Eggs on bedding, clothing, towels, toys, food or other items can be picked up and swallowed. The CDC notes the eggs can survive two to three weeks on objects that are not washed or cleaned.
• Through the air, rarely. The tiny eggs can float in the air and be breathed in and swallowed.

Because the eggs can be swallowed again by the same person, someone with pinworm can also re-infect themselves. That is one reason the CDC advises treating the infected person, their household and their caregivers at the same time. Our pinworm life cycle page walks through each stage.

Pinworm at home, school and work

Pinworm often shows up in more than one person in a home, and repeat infections are common among household members and among children who play together at childcare or school. Whether someone should stay home is a question for their clinician or the school, childcare center or employer's own policy. The CDC's prevention advice focuses on handwashing, nail care, morning bathing and laundry rather than on keeping people apart.

Can you get pinworms from pets, pools or toilet seats?

• Pets: no. The CDC says you can't get pinworm from your pets or give your pets pinworm. Pinworm is a human parasite.
• Swimming pools: very unlikely. The CDC says you are extremely unlikely to get pinworm in a swimming pool.
• Toilet seats and other surfaces: eggs can survive on household objects, so a shared bathroom is one of many surfaces where eggs can land. Washing hands after using the toilet and before eating is the CDC's main defense.

Roundworm, whipworm and hookworm: spread through soil

The CDC groups these three as soil-transmitted helminths. An infected person passes eggs in their stool, and the eggs reach soil where people defecate outdoors, where sanitation is poor, or where human stool is used as fertilizer. The CDC says these infections are found mainly in warm, moist places where sanitation and hygiene are poor, and they are uncommon in the United States.

What matters for contagiousness is the soil step:

• Roundworm and whipworm eggs become infective only as they mature in soil. People are infected by swallowing those eggs, for example on fruits or vegetables that were not carefully washed, peeled or cooked, in contaminated drinking water, or on unwashed hands.
• Hookworm eggs hatch in soil, and the larvae grow into a form that can get through human skin. The CDC says you cannot get hookworm from hookworm eggs, and that it spreads mainly by walking barefoot on contaminated soil. One kind of hookworm can also be caught by swallowing the larvae.

Because of that soil step, a person with one of these worms does not pass it straight to the people they live or work with in the way pinworm spreads. The risk comes from contaminated soil, food or water, which is why it is tied mostly to living in, or traveling to, places where these worms are common. Our guide to parasites from traveling explains how travelers are exposed. For more on each one, see roundworm in humans, whipworm in humans and hookworm in humans.

Strongyloides: usually soil, rarely person to person

Strongyloides larvae live in soil and get in through exposed skin, such as bare feet. The CDC notes that some of the young worms can re-infect the same person from inside the gut or around the anus, which is why the infection can last for years.

Person-to-person spread is rare. The CDC lists organ transplants, long-term care facilities, facilities for people who need help with daily personal care, and daycare centers as the settings where it has happened. People with a weakened immune system, or who take steroids or other medicines that weaken immunity, can become severely ill from it and should be assessed in person. See strongyloidiasis symptoms and treatment for more.

River blindness: spread by blackflies, not people

Onchocerciasis is caused by a microscopic worm, but it is not passed between people. The CDC explains that it spreads through the bites of infected blackflies, which breed near streams and rivers, mostly in rural sub-Saharan Africa. It takes repeated bites to become infected, so it rarely affects short-term travelers. Our page on onchocerciasis (river blindness) has the detail.

Can humans catch worms from dogs and cats?

Not human pinworm. Animals do carry their own worms, though, and a few of them can affect people:

• Dog and cat roundworm (Toxocara) can reach people who swallow eggs from soil or hands contaminated with pet feces. The CDC says toxocariasis does not spread from person to person like a cold or the flu.
• Dog and cat hookworm larvae in soil or sand can burrow into bare skin and cause itchy, red tracks. These animal hookworms are different from the human hookworm that lives in the intestine.

Picking up pet waste promptly, washing hands after handling animals or soil, and keeping pets under regular veterinary care lower the chances of these infections. A clinician should look at any rash or symptoms you think came from an animal.

How to lower the chance of spreading worms

The CDC's advice comes down to a few habits:

• Wash your hands with soap and warm water after using the toilet or changing diapers, and before handling food
• Keep fingernails short and clean, and try not to scratch around the anus or bite your nails
• With pinworm in the home, bathe in the morning, change underwear daily, don't share washcloths, and wash nightclothes, towels and bedding in hot water without shaking them out
• Have children bathe separately, and take showers instead of tub baths
• Wash, peel or cook raw fruits and vegetables
• Wear shoes where soil may be contaminated with human or animal stool
• Pick up pet waste promptly

When to see a clinician

A clinician can confirm which worm, if any, is involved. Pinworm is usually found with a pinworm tape test, and most other intestinal worms with a stool test for parasites. See a clinician in person, rather than online, if you have blood in your stool, severe or worsening belly pain, a high fever, signs of dehydration, a weakened immune system, or you are pregnant or breastfeeding. Children should see their own pediatrician.

Getting a prescription through Get It Prescribed

If a clinician has diagnosed one of these infections, or a household member has been diagnosed and you have the same symptoms, a licensed provider can review a written health assessment through Get It Prescribed and decide whether mebendazole or ivermectin is appropriate for a labeled use. Mebendazole's labeled uses are pinworm, whipworm, roundworm and hookworm; ivermectin's are intestinal strongyloidiasis and onchocerciasis. No prescription is guaranteed, and the provider may recommend testing or an in-person visit instead. How it works shows each step.

The medicines dispensed through Get It Prescribed are compounded preparations made by a licensed compounding pharmacy. They are not FDA-approved, the FDA has not reviewed them for safety, effectiveness or quality, and they are not generics of, or substitutes for, the brand-name products.

The cost is a one-time $50 provider consultation fee, plus $3.00 per ivermectin tablet or $3.50 per mebendazole capsule if a prescription is issued, with the quantity decided by the provider. The service is for adults and is available in all 50 states and the District of Columbia; some states require a live phone or video visit.

This article is general education, not medical advice. It does not replace an evaluation by a licensed clinician who knows your history.

Related questions

How do pinworms spread from person to person?

Mostly from hands to mouth. Eggs laid around the anus get onto fingers, under fingernails, or onto bedding, clothing and other objects, and are then swallowed. The CDC says the eggs can survive two to three weeks on objects that are not cleaned, and rarely they are breathed in from the air.

Can you get pinworms from a dog or cat?

No. The CDC says people can't get pinworm from their pets or give pinworm to their pets, because pinworm is a human parasite. Dogs and cats carry other worms, such as Toxocara roundworm and animal hookworm, which spread through contaminated soil or sand, not through pinworm eggs.

Is roundworm contagious between people?

Not directly. Roundworm eggs passed in stool have to mature in soil before they can infect someone, so the risk comes from contaminated soil, food or water rather than from close contact with an infected person. Whipworm spreads the same way.

Can you catch hookworm from another person?

Not by contact. Hookworm eggs hatch in soil, and the larvae get in through bare skin, most often the feet, so the CDC's main advice is to wear shoes where soil may be contaminated with human stool.

Should everyone in the house be treated for pinworm?

The CDC advises treating the infected person, their household members and their caregivers at the same time, because pinworm spreads easily within a home and repeat infections are common. A clinician decides what each person needs.

Sources

• CDC: About Pinworm Infection — who gets pinworm, how it spreads, and household treatment.
• CDC: Preventing Pinworm Infection — handwashing, laundry and bathing steps, and that pets and pools are not a source.
• CDC: About Soil-transmitted Helminths — how roundworm, whipworm and hookworm spread through soil.
• CDC: About Hookworm — how hookworm larvae enter through the skin.
• CDC: About Whipworms — how whipworm eggs become infective in soil.
• CDC: About Strongyloides — soil exposure and the rare settings for person-to-person spread.
• CDC: About Onchocerciasis — spread by blackfly bites.
• CDC: About Toxocariasis — roundworm from dogs and cats, and that it does not spread person to person.
• CDC: About Zoonotic Hookworm — animal hookworm larvae in soil and sand.
• MedlinePlus: Pinworms — consumer overview from the National Library of Medicine.
• DailyMed: mebendazole chewable tablet prescribing information — labeled uses: pinworm, whipworm, roundworm and hookworm.
• DailyMed: ivermectin tablet prescribing information — labeled uses: intestinal strongyloidiasis and onchocerciasis.
• FDA: Compounding and the FDA — Questions and Answers — what compounded preparations are and how they are regulated.