On Sunday, the South Dakota Department of Health announced that travelers from the four southern states who tested positive for Ebola in the past month are now prohibited from traveling to any state.

South Dakota is one of six states in the U.S. with restrictions in place to stop the spread of the deadly virus, which was first detected in Guinea in March and has since spread throughout Africa.

“The quarantine has been implemented because of the heightened risk of transmission for travelers who are already infected,” said Dr. James Anderson, director of the South Dakotas Health Department.

“We’re also making sure people are getting the proper medical care.”

The ban applies to anyone from Liberia, Sierra Leone, Guinea, or Nigeria, as well as those who tested negative to Ebola, and to anyone traveling from countries with the following countries: Angola, Algeria, Benin, Botswana, Cameroon, Chad, Central African Republic, Congo, Equatorial Guinea, Gabon, Ghana, Guyana, Haiti, Honduras, Jamaica, Mali, Mauritania, Niger, Nigeria, Senegal, South Africa, Tanzania, Uganda, Zambia, Zimbabwe.

“South Dakotans should remain vigilant,” Anderson said.

“I hope this helps.”

According to the Department of State, there were about 2,400 cases of Ebola in South Carolina between June 15 and Aug. 3, and more than 9,000 people have died in the country from the virus.

Since the beginning of the outbreak in the United States, more than 7,000 Americans have been infected with the virus, including more than 2,300 deaths.