The World Health Organization (WHO ) declared the coronavirus crisis a “pandemic ” on March 11 of 2020 .
He was reminding people that the word is used only for the most extreme and dangerous spreads of disease .
The number of deaths from the disease is about 4.7 million .
At the same time , new versions , or variants , of the SARS-CoV-2 virus that causes COVID-19 are developing and spreading very fast .
In the United States , the Centers for Disease Control and Prevention (CDC ) said the Delta variant is the main cause of new COVID infections .
Governments and health officials around the world reacted to the crisis by establishing the largest vaccination program in history .
Data collected by the Bloomberg company shows that by September , more than 5.9 billion shots of vaccine have been administered to people across 184 countries .
Michael Osterholm is an expert on epidemics at the University of Minnesota in Minneapolis .
He told Nature that ending the existence of the virus right now is unrealistic .
He compared it to trying to build “a stepping-stone pathway to the Moon .”
The World Health Organization defines pandemics , epidemics , and endemics based on a disease's rate of spread .
For example , the Ebola outbreak that spread within West African countries from 2014-2016 was called an epidemic .
In 2016 , the world's health agency declared that the Zika virus was a “Public Health Emergency of International Concern .”
The insects called mosquitos pass the disease to humans when they bite them .
Zika was first discovered in Africa and Asia before spreading to Brazil and other South American countries .
Some considered Zika an epidemic while others view it as a pandemic like the current coronavirus health crisis .
The difference between an epidemic and a pandemic is not in the severity of the disease , but the degree to which it has spread .
A pandemic means a disease has spread to several countries around the world .
Epidemic is used to mean disease spreads in smaller areas .
The word endemic came from the Greek word endēmos , meaning “in the population .”
In public health , it is used to describe a disease outbreak that is present and limited to an area .
This makes the disease spread and rates easier to control .
Malaria , for example , is considered an endemic in many warm , wet areas across countries in Asia , Africa , and South America .
The H1N1 influenza virus is also endemic .
Christopher Dye studies epidemics at Britain's University of Oxford .
They wrote about the disease in the online news site The Conversation .
The scientists said that with face coverings and vaccination , the COVID-19 pandemic “could disappear like smallpox or polio did ….”
But they said the disease could also become endemic over time .
They said viruses are more likely to become endemic if they are adapted to “a local environment ” of people with “low or zero immunity .”
And vaccination rates will affect the progress of the disease .
A low vaccine rate could permit the virus to continue at an epidemic level for longer , they wrote .