The World Health Organization has officially declared COVID-19, the disease caused by the novel coronavirus, a pandemic.

The virus, which originated in China, has infected more than 113,000 people worldwide and killed more than 4,000, according to the WHO.

In the U.S., more than 930 people have been infected and at least 29 people have died across 28 states and Washington, D.C.

The U.S. Centers for Disease Control and Prevention defines a pandemic as an epidemic — a sudden increase in the number of cases of a disease — that has “spread over several countries or continents, usually affecting a large number of people.”

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"We have therefore made the assessment that #COVID19 can be characterized as a pandemic"-@DrTedros #coronavirus pic.twitter.com/JqdsM2051A — World Health Organization (WHO) (@WHO) March 11, 2020

“Pandemic is not a word to use lightly or carelessly,” WHO Director-General Tedros Adhanom Ghebreyesus said during a news conference in Geneva on Wednesday. “It is a word that, if misused, can cause unreasonable fear, or unjustified acceptance that the fight is over, leading to unnecessary suffering and death.”

“Describing the situation as a pandemic does not change WHO’s assessment of the threat posed by this coronavirus,” he added. “It doesn’t change what WHO is doing, and it doesn’t change what countries should do.”

Ghebreyesus stressed that evidence suggests this coronavirus can be controlled if appropriate measures are taken by each country.

“The challenge for many countries who are now dealing with large COVID-19 clusters or community transmission is not whether they can do the same — it’s whether they will,” Ghebreyesus said.

“We are grateful for the measures being taken in Iran, Italy and South Korea to slow the virus and control their COVID-19 epidemics,” he continued. “We know that these measures are taking a heavy toll on societies and economies, just as they did in China.”

Democrats and health experts have criticized President Donald Trump’s response to the spread of coronavirus. He has consistently downplayed its severity and spread misinformation about the virus. Last week, he claimed a vaccine for the virus would be developed “soon.” In fact, federal health officials expect it will be at least a year until a vaccine is ready.