What is an Endemic Disease?

Malaria Infected Red Blood Cells
Malarial Parasites Infecting three Red Blood Cells, Plasmodium vivax, 500X at 35mm. Three infected cells are clearly shown, the ring stage is in the center. Chills and fever of malaria are correlated with the bursting of the RBCs. Ed Reschke/Getty Imges

The Definition of an Endemic Disease

An endemic disease is a disease that is always present in a certain population or region. One of the most talked about endemic diseases is malaria. Malaria is such a fixture in certain parts of Africa that a protective mutation - sickle cell trait - has become common in local populations.

Endemic diseases are often confused with epidemics. However, an epidemic refers to an outbreak of a disease that is spreading through one or more populations.

In contrast, an endemic disease is one that is constantly present in a group or geographic area. Pandemics are world wide epidemics. Under certain circumstances, an epidemic can lead to a disease becoming endemic.

Endemic diseases are not always present at high levels. They can be relatively rare. The defining feature of a regional endemic disease is that it can always be found in the population that lives there.

Examples: Malaria is endemic in many areas of Africa.

Are Any STDs Endemic?

In certain areas of the world there are several STDs that could be considered endemic. For example, HIV is considered to be endemic in many parts of Africa. At this point, and for the conceivable future, eradication is unlikely. That's true even as improving treatment is starting to bring the HIV epidemic under control. 

Hepatitis B (HBV) is also endemic throughout the world. Although HBV is not always a sexually transmitted disease, it can be sexually transmitted.

Fortunately, there is a vaccine available to prevent hepatitis B transmission. 

Syphilis used to be endemic. Fortunately, effective treatments have gone a long way in reducing the number of people infected by this disease. Unfortunately, partially due to spread through oral sex, syphilis has recently been on the rise.

It's unlikely that it will become endemic again. However, it can still lead to significant problems -- particularly for newborns


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