Hookworms spread when microscopic larvae in contaminated soil penetrate bare skin, typically through the feet. The cycle begins when an infected person or animal passes hookworm eggs in their stool, and those eggs hatch into larvae that wait in warm, moist soil for a new host. You cannot catch hookworms from casual contact with another person or from touching surfaces indoors.
From Egg to Infectious Larva
Hookworm eggs leave the body in feces. When those eggs land in warm, moist, shaded soil, they hatch within one to two days. The newly hatched larvae are not yet dangerous. They need 5 to 10 days of feeding and growing in the soil before they molt twice and reach their infectious stage, called the filariform or third-stage larva. At this point, they’re roughly 500 to 700 micrometers long, barely visible to the naked eye, and capable of rapidly burrowing through intact human skin.
This is why hookworm thrives in tropical and subtropical regions with poor sanitation. Where human or animal waste contaminates outdoor soil, and the climate stays warm and humid, the larvae have exactly the conditions they need to develop and survive while waiting for a host.
How Larvae Enter the Body
The primary route is through bare skin. When you walk barefoot on contaminated ground, the larvae penetrate most commonly through hair follicles on the feet or between the toes. Sitting or lying on contaminated soil with exposed skin also works. The larvae don’t need a cut or wound to get in. They burrow through normal, healthy skin on their own.
One species of human hookworm can also spread through oral ingestion, when larvae are accidentally swallowed with contaminated food or water. But skin penetration remains the dominant route for most infections worldwide.
What Happens After They Get In
Once through the skin, hookworm larvae take a surprisingly long journey through the body before settling in the gut. They enter the bloodstream through the dermis and travel to the lungs within about 10 days. In the lungs, they break into the tiny air sacs and are carried upward by the sweeping motion of the respiratory tract’s lining cells. When they reach the throat, they get swallowed, often without the person noticing.
From the throat, they travel down to the small intestine, where they undergo two more developmental stages and grow into adults with specialized mouthparts for attaching to the intestinal wall. Adult hookworms feed on blood, which is why chronic infections cause iron deficiency and anemia over time. Adults can live in the gut for years, producing thousands of eggs daily that pass out in stool to restart the cycle.
Symptoms and Timeline
The first sign is often “ground itch,” an itchy, red rash at the spot where larvae burrowed in. This typically appears within a few days of skin contact, though it can sometimes take weeks. As the worms migrate through the lungs, some people develop a mild cough, but most have no respiratory symptoms at all.
Gut symptoms take longer to appear because the worms need time to travel, mature, and start feeding. Abdominal pain, diarrhea, and fatigue from blood loss develop gradually. Light infections may produce no noticeable symptoms for months. Heavy infections, especially in children or people with poor nutrition, can cause significant anemia and developmental problems.
Animal Hookworms and Skin Tracks
Dogs and cats carry their own species of hookworm, and these can spread to people the same way: larvae in contaminated soil or sand burrow into bare skin. The difference is that animal hookworms generally cannot complete their life cycle in a human body. They get stuck wandering under the skin, unable to reach the gut.
This produces a condition called cutaneous larva migrans. It shows up as intensely itchy, raised red lines that trace irregular tracks across the skin, marking the path of the lost larva. Beaches, sandboxes, and parks where pets defecate are common sources. The median time from skin contact to visible tracks is 10 to 15 days. The good news is that the larvae eventually die on their own and symptoms resolve within several weeks, though treatment can speed that up. In rare cases, animal hookworms migrate into deeper tissue in the intestine, lungs, or eye.
Who Is Most at Risk
Hookworm infection is one of the most common parasitic diseases on the planet. The WHO reported that more than 883 million children required preventive treatment for soil-transmitted parasites (including hookworm) in 2024. South-East Asia carries the heaviest burden, with nearly 484 million children needing treatment, followed by Africa at 250 million. The Americas, Eastern Mediterranean, and Western Pacific regions are also affected.
Within any region, risk concentrates among people who regularly contact bare soil in areas with poor sewage systems or open defecation. Agricultural workers, children who play outside barefoot, and communities without access to toilets face the highest exposure.
How to Prevent Infection
Wearing shoes is the simplest and most effective personal protection. Research published in The American Journal of Tropical Medicine and Hygiene estimates that consistent shoe-wearing lowers the odds of hookworm infection by 18% to 61%, depending on the study. In communities where shoes were distributed, the frequency of shoe-wearing rose by 25%, which researchers projected would translate to meaningful drops in infection rates.
Beyond shoes, the bigger picture is sanitation. Hookworm cannot spread without fecal contamination of soil. Proper toilets, sewage treatment, and avoiding the use of untreated human waste as fertilizer break the cycle at its source. If you’re traveling in a tropical area, avoid walking barefoot on soil or sand, especially near areas where sanitation is uncertain. The same applies to beaches where dogs roam freely. Sitting on a towel or mat rather than directly on sand reduces your risk of picking up animal hookworm larvae.