Over the past three days, the CDC has also issued new travel notices for Pakistan, Turkey, Canada, Brazil, Japan, Israel and Australia

The U.S. Centers for Disease Control and Prevention (CDC) have raised their travel warning for several new countries to a Level 3 — their highest alert level — on Monday amid the coronavirus (COVID-19) pandemic.

According to the CDC, travelers should avoid all nonessential travel to Thailand, Chile, Pakistan and Turkey as the countries are “experiencing widespread ongoing transmission of a respiratory illness caused by the novel (new) coronavirus,” according to notices on its website.

“Widespread ongoing transmission means that people have been infected with the virus, but how or where they became infected is not known, and virus transmission is ongoing in many communities across a country or region,” the notices read.

The CDC recommends those who traveled to these countries in the last two weeks to stay home, monitor their health, and practice social distancing for 14 days.

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The warning comes just two days after the CDC issued similar travel notices to Canada, Israel, Japan, Australia and Brazil, urging the public to avoid all nonessential travel to these countries due the spread of coronavirus within its respective borders.

Malaysia, Iran, South Korea, China, the United Kingdom, Ireland and 29 different countries in Europe also received Level 3 travel notices earlier this month.

As of Monday evening, there have been at least 366,000 confirmed cases of the coronavirus and 16,239 deaths reported in 163 countries around the world, according to a New York Times database.

The first cases of a mysterious respiratory illness — what is now known as COVID-19, a form of coronavirus — began in Wuhan, China in late December. Since then, the virus has spread worldwide, leading the World Health Organization to declare a public health emergency, the first since the zika epidemic in 2016.

At first, this coronavirus was contained to China, but Wuhan is a major transportation hub with hundreds of flights leaving and landing from the city of 11 million each day. Soon, as people flew from the area to different countries, the coronavirus reached more countries, including the United States.

Coronavirus Maps
Coronavirus cases worldwide as of March 23

During a March 9 press briefing, a top official from the CDC said that “many will become sick” from the coronavirus as it spreads throughout the U.S.

“It’s fair to say that as the trajectory of the outbreak continues, many people in the United States, will at some point in time, either this year or next, be exposed to this virus. And there’s a good chance that many will become sick,” said Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases.

Based on data from the World Health Organization’s research in China, Messonnier said that COVID-19 is “highly contagious.”

“And there’s essentially no immunity against this virus in the population, because it’s a new virus,” she said.

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Messonnier emphasized, however, that the disease will be mild for the majority of people, with symptoms such as coughing, sneezing and a fever.

A more severe case would be a respiratory infection, similar to pneumonia, that can lead to death. Messonnier said that older adults are at the highest risk.

“Starting at age 60, there is an increase in the risk of disease, and the risk increases with age,” she said. “The highest risk of serious illness and death is in people over 80 years. People with serious underlying health conditions also are more likely to develop serious outcomes, including death. The people who are at greatest risk are those who are older, and who also have serious long-term health conditions like diabetes, heart disease or lung disease.”

As information about the coronavirus pandemic rapidly changes, PEOPLE is committed to providing the most recent data in our coverage. Some of the information in this story may have changed after publication. For the latest on COVID-19, readers are encouraged to use online resources from CDC, WHO, and local public health departments and visit our coronavirus hub.