What is an Epidemic?
An epidemic occurs when an unusually large number of people in a community get sick at the same time. Examples of epidemic diseases include typhus, influenza, the Black Death, malaria, and smallpox.
What causes an Epidemic?
There are a number of events that can trigger an epidemic.
Infected food and water – An outbreak can begin if food or water becomes contaminated. If a city’s local water supply becomes infected, some people in the city will get sick, causing an epidemic.
Increased virulence of the disease – Sometimes the pathogen (germ) that causes the disease can change and become more virulent. This means it can more easily infect people and make them sick.
Introduction of a new disease – Many outbreaks begin when a new disease is introduced into a population. This happened when Europeans brought smallpox to the Americas, killing up to 90% of the native population.
Lower resistance to a disease – Sometimes starvation and a poor diet can make a population less resistant to a disease that causes an epidemic.
Natural disasters and wars – Natural disasters and wars can trigger disease outbreaks by contaminating water supplies, creating new diseases, and reducing people’s resistance to disease.
How does Disease spread?
Disease can spread and be transmitted in many ways, including:
Insects – Insects can carry disease and spread it from person to person. Examples of diseases caused by insects include plague and malaria.
Airborne transmission – Infection can also be spread through the air, usually when a person coughs or sneezes. Examples of airborne diseases include influenza, measles, and tuberculosis.
Foods and water – Some diseases can be spread through contaminated food or water. Examples include cholera, dysentery and typhoid fever.
How do they end?
Although epidemics can spread quickly and kill millions, they eventually end. There are different reasons why an outbreak can end:
Fewer Hosts – When an epidemic breaks out, it can strike the weakest and most susceptible. These people may die or survive. If these people survive, they may develop immunity against the disease. Over time, the disease finds fewer and fewer hosts it can easily attack. Eventually, the epidemic slowed down and ended.
Seasonal – Some diseases are seasonal. For example, the flu spreads more easily during the winter and tends to disappear in the spring.
Fewer Carriers – Sometimes carriers can be inactive. An example of this is mosquito-borne malaria. Mosquitoes become inactive in cold weather or in winter.
What is a Pandemic?
A pandemic is an epidemic that has spread over a large area, often across multiple continents or worldwide.
Six Stages of a Pandemic
The World Health Organization (WHO) describes six stages of a virus pandemic:
Viruses are found in animals, but not in humans.
Viruses have been found in humans.
There are small clusters of the disease, but it doesn’t spread quickly.
The virus is transmitted from person to person and there are community outbreaks of the disease.
The virus has spread to at least two countries. An official pandemic is imminent.
The disease is currently classified as a pandemic.