What are endemic, epidemic and pandemic ?
It is said that there is an endemic (from Greek en = em; demos = people) in a population if an infectious contagious disease is maintained in a population without external contamination. The chickenpox , for example, is endemic in the UK, but the malaria not. Although malaria can occur in the UK, the disease does not persist due to the lack of the vector necessary for the transmission process. In general, the endemic is of a continuous nature and restricted to a certain area, such as endemic areas of yellow fever and dengue in Brazil, or of hepatitis A, in the USA or Portugal. Endemic disease is therefore a local disease. It has a continuous permanence, but it does not reach or spread to other communities. People traveling to regions where there are endemic diseases need to be vaccinated against them.
It is said that there is an epidemic when a transmissible infectious disease that occurs in a region spreads rapidly among people from other regions, giving rise there a great number of cases of the disease, called epidemic outbreak. The epidemic usually occurs because of a mutation in the disease-transmitting agent or the onset of a new, unknown agent. The occurrence of a single case of a communicable disease in a place where it did not exist or the first case of a hitherto unknown disease require rigorous investigation measures as they represent a danger of causing an epidemic. The flu avian and infection by viruses Ebola are recent examples of the epidemic.
There is a pandemic when a contagious disease spreads in large proportions, on one or more continents or around the world, causing countless deaths and eventually destroying entire cities or regions. A pandemic occurs due to the appearance of a new disease for which the population has no resistance or when the infectious agent spreads easily. AIDS and the Spanish flu , for example, are examples of pandemics. The cancer is a disease spread all over the world, responsible for numerous deaths but is not considered a pandemic because it is not a disease contagious .
What are the differences between endemic, epidemic and pandemic ?
If a disease exists only in a certain area it is said to be endemic; if the disease is transmitted to other populations and infests more than one region, it is said that there is an epidemic; if the disease spreads uncontrollably, spreading over the continents or around the world, there is a pandemic . An endemic can evolve into an epidemic and, on the contrary, a disease can pass from epidemic to endemic and highly contagious and deadly diseases, although localized, have the potential to become a pandemic .