Parasites are everywhere. In fact, there are more parasites in the world than any other kind of organism. They are on all continents, in all oceans. Some parasites are harmless, but many can cause serious harm to humans and animals. Parasitic diseases are widespread. About 70 percent of the world's rural inhabitants live in areas where at least one parasitic disease is common. Malaria kills as many as 2 million people every year. Most parasitic diseases can be prevented with good hygiene and sanitation, but these medical resources are often hard to find in rural areas where infections are most common. Parasites can spread through mosquito bites and contaminated water sources, including drinking water and swimming pools, or by food sources such as pork or beef that hasn't been properly cooked."