Epidemics and pandemics: how far a disease spreads

0:00How far can a disease spread, and how does it affect people?

0:05Infectious diseases are caused by pathogens, germs such as bacteria and viruses, that pass from person to person.

0:15On the map, each red dot marks cases: people who have caught the disease.

0:20When more people than usual catch a disease in one place, such as a town, it is called an outbreak.

0:29If it spreads to many people across a whole region or country, it is called an epidemic.

0:36Smallpox and measles have caused many deadly epidemics.

0:41When infected people travel, they can carry the pathogen to other continents.

0:46A disease that spreads across several continents is called a pandemic.

0:52In 1918, a flu pandemic infected about one in three people in the world.

0:58It killed at least 50 million people.

1:02Its nickname, Spanish flu, is misleading: there is no evidence it began in Spain, and where it began is still unknown.

1:11In 2003, a disease called SARS reached 29 countries, but there were only about 8,000 cases.

1:20Quick action, such as isolating sick people to keep them away from others, stopped it spreading further.

1:28Epidemics and pandemics can cause many deaths, full hospitals, closed schools and businesses, and new public health rules.

1:38An outbreak is in one place, an epidemic covers a region, and a pandemic spreads across several continents.