Epidemic: An outbreak of disease that attacks many peoples at about the same time and may spread through one or several communities.
Pandemic: When an epidemic spreads throughout the world.
People: Droplet infection (coughing, sneezing), direct contact (kissing), indirect contact.
Animals: Fleas and rats spread the bubonic plague in 1348. 1/3 Europe died! (An estimated 20 million people died) Mosquitoes in Africa and Latin America spread malaria. Ticks spread Lyme disease. Ducks and pigs can carry flu viruses.
Nonliving sources: Disease can be transmitted in contaminated food and water. For instance, salmonella can be found in meat. Hazardous chemicals can cause cancers