What is it: hookworm is an intestinal parasite of humans that usually causes mild diarrhoea or cramps. Heavy infection with hookworm can create serious health problems for newborns, children, and pregnant women. Hookworm infections occur mostly in tropical and subtropical climates and are estimated to infect about 1 billion people — about one-fifth of the world's population. One of the most common species is found in southern Europe, northern Africa, northern Asia, and parts of South America. Hookworm eggs require warm, moist, shaded soil to hatch into larvae. The larvae are hardly visible and penetrate the skin (often through bare feet), and are carried to the lungs. Then they go through the respiratory tract to the mouth where they are swallowed, and eventually reach the small intestine. This journey takes about a week. In the small intestine, the larvae develop into half-inch-long worms, attaching themselves to the intestinal wall, where they suck blood. The adult worms produce thousands of eggs. These eggs are passed in human faeces (stools).

How do I get it: you can become infected by direct contact with contaminated soil, usually by walking barefoot, or accidentally swallowing contaminated soil. Children in the countries or areas above are most likely at risk because they often play in dirt and go barefoot. Since transmission of hookworm infection requires development of the larvae in soil, hookworm cannot be spread person to person.

What happens if I get it: itching and a rash at the site of where the skin touched soil or sand is usually the first sign of infection. These symptoms occur when the larvae penetrate the skin. While a light infection may show no symptoms, heavy infection can cause anaemia, abdominal pain, diarrhoea, loss of appetite, and weight loss. Heavy, chronic infections can cause stunted growth and mental development.

Diagnose and treatment: the infection is diagnosed by identifying hookworm eggs in a stool sample. Hookworm infections are generally treated for 1-3 days with medication prescribed by your health care provider.

How can I avoid contracting hookworm: don't not walk barefoot or have contact with the soil with bare hands in areas where hookworm is common or there is likely to be faeces in the soil or sand.