WASHINGTON — On Wednesday, the United States imposed new constraints on on people entering the country from three nations at the center of West Africa’s Ebola epidemic, mandating that they report their temperature daily and stay in touch with health authorities.

President Obama expressed cautious optimism about the situation in the United States after meeting with his Ebola response coordinator, Ron Klain, and other top officials on Klain’s first day on the job since being named on Friday.

The U.S. Centers for Disease Control and Prevention’s new restrictions on travelers arriving from Liberia, Sierra Leone and Guinea marked the latest precautions put in place by the Obama administration to stop the spread of the virus. The steps stopped short of a ban on travelers from those countries demanded by some lawmakers.

The CDC said that, beginning on Monday, travelers from the three countries will be told to check in with health officials every day and report their temperatures and any Ebola symptoms for 21 days, the period of incubation for the virus.

The travelers will be required to provide emails, phone numbers and addresses for themselves and for a friend or relative in the United States covering the 21 days, and the information will be shared with local health authorities.

The travelers also will be required to coordinate with local public health officials if they intend to travel within the United States. If a traveler does not report in, local health officials will take immediate steps to find the person.

CDC Director Dr. Tom Frieden told reporters the active monitoring program will remain in place until the outbreak in West Africa is over. The U.N. World Health Organization’s latest figures on Wednesday showed at least 4,877 people out of 9,936 confirmed, probable and suspected cases have died in the outbreak, the worst on record.

Beginning Wednesday, travelers from Liberia, Sierra Leone or Guinea were being funneled through one of five major U.S. airports conducting increased screening for the virus.

Six states account for nearly 70 percent of all travelers arriving from the affected countries: New York, Pennsylvania, Maryland, Virginia, New Jersey and Georgia. The new monitoring will begin in those states first and will be expanded to other states.

The CDC said the monitoring program affects anyone coming back from the region, including CDC employees and journalists. It said when affected travelers enter one of the five airports they will receive a care kit that contains a tracking log, a pictorial description of symptoms, a thermometer, instructions on how to monitor their temperature and information on what to do if they experience symptoms.