Photos: Ebola outbreak

A picture taken Nov. 7 shows people walking past a billboard with a message about ebola in Freetown, Sierra Leone.  (Francisco Leong/AFP/Getty Images)

In this Wednesday, Sept. 24, 2014 file photo, healthcare workers load a man suspected of suffering from the Ebola virus onto an ambulance in Kenema, Sierra Leone.  (Tanya Bindra / AP file photo)

An empty area outside an Ebola virus recovery ward in Freetown, Sierra Leone. The World Health Organization says officials are now focused on ending the biggest-ever Ebola outbreak rather than just slowing the virus’ spread.  (Michael Duff / AP)

A convoy carrying a nurse, who has been diagnosed with the Ebola virus, arrives at The Royal Free hospital in London, England, on Dec. 30.  (Peter Macdiarmid/Getty Images)

A general view of the Royal Free Hospital where a female healthcare worker who contracted the Ebola virus is being treated in London on Dec. 30  (John Stillwell/AP)

Medical staff at Glasgow airport in Scotland in protective gear transport a healthcare worker diagnosed with Ebola during her transfer to the Royal Free Hospital in London on Dec. 30.  (Danny Lawson/AP)

The U.S. Centers for Disease Control and Prevention headquarters in Atlanta.

Sierra Leonean doctors practice wearing protective clothing in the Ebola Training Academy in Freetown, Sierra Leone.  (BAZ RATNER/Reuters)

Martin Salia, a Sierra Leonean doctor, died of Ebola on Nov. 17 after being flown to Nebraska for treatment.  (Handout / Reuters)

After being released from the hospital in New York City on Nov. 11, Dr. Craig Spencer, now virus-free, greets some of the Bellevue staff members who treated him after he was diagnosed with Ebola.   (Spencer Platt / Getty Images)

Ebola survivor Nina Pham is reunited with her dog Bentley at the Dallas Animal Services Center in Dallas, November 1, 2014.  (Lisa Maria Garza / Reuters)

U.S. Ambassador to the United Nations Power gets her temperature taken at John F. Kennedy airport in New York.  (Michelle Nichols/Reuters)

Ebola virus discoverer Peter Piot addresses a news conference at the United Nations in Geneva October 7, 2014.   (Denis Balibouse / Reuters)

Kaci Hickox and boyfriend Ted Wilbur go for a bike ride in Fort Kent, Maine October 30, 2014.   (Ashley L. Conti / Reuters)

Kaci Hickox returns to her home surrounded by media after going for a bike ride with boyfriend Ted Wilbur in Fort Kent, Maine October 30, 2014.   (Ashley L. Conti / Reuters)

Soldiers wear protective suits as members of the 101st Airborne Division (Air Assault), who are earmarked for the fight against Ebola, conduct training before their deployment to West Africa, at Fort Campbell, Kentucky October 9, 2014.   (Harrison McClary / Reuters)

A transmission electron micrograph shows Ebola virus particles in this undated handout image released by the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) in Fredrick, Maryland.  (Handout / Reuters)

President Barack Obama hugs Dallas nurse Nina Pham at the Oval Office in Washington, October 24, 2014.   (LARRY DOWNING / Reuters)

Director of the National Institute of Allergy and Infectious Diseases Anthony Fauci leaves with Nina Pham, the nurse who was infected with Ebola, after a news briefing at National Institutes of Health October 24, 2014 in Bethesda, Maryland. Pham, who first diagnosed on October 12, was declared free of the virus on Friday.   (Alex Wong / Getty Images)

Nina Pham speaks during a news briefing at the National Institutes of Health October 24, 2014 in Bethesda, Maryland. Pham, who was first diagnosed with Ebola on October 12, was declared free of the virus on Friday.   (Alex Wong / Getty Images)

Nina Pham participates during a news briefing as Pham’s mother Diana (4th L) and sister Cathy (2nd L), and Director of NIH Clinical Center John Gallin (L) look on at the National Institutes of Health October 24, 2014 in Bethesda, Maryland.  (Alex Wong / Getty Images)

Texas nurse Nina Pham is shown in this still image taken from video in her isolation room at Texas Presbyterian Hospital in Dallas. Pham was declared virus-free on Friday, October 24, 2014.  (Handout / Reuters)

New York Mayor Bill de Blasio (C) and New York Governor Andrew Cuomo (R) attend a news conference in Bellevue Hospital in New York October 23, 2014. A physician with Doctors Without Borders (MSF) who returned to New York City after treating Ebola victims in West Africa tested positive for the virus, setting off fresh fears about the spread of the disease. Dr. Craig Spencer, 33, is in isolation at Bellevue Hospital. Two friends and his fiancée have been quarantined. At a news conference, de Blasio sought to reassure the public that they are safe from Ebola. REUTERS/Eduardo Munoz (UNITED STATES - Tags: HEALTH POLITICS) ** Usable by BS, CT, DP, FL, HC, MC, OS, HOY, CGT and CCT **  (EDUARDO MUNOZ / Reuters Photo)

Riqui Lawrence looks up towards his apartment after speaking to the media about his concerns after it was confirmed that his neighbour, Dr. Craig Spencer, contracted Ebola, in New York.   (CARLO ALLEGRI / Reuters)

U.S. Coast Guard Health Technician Nathan Wallenmeyer (L) and Customs Border Protection (CBP) Supervisor Sam Ko conduct prescreening measures on a passenger arriving from Sierra Leone at O’Hare International Airport’s Terminal 5 in Chicago, in this handout picture taken October 16, 2014.   (Handout / Reuters)

A photograph made available by US Customs and Border Protection on 17 October 2014 shows CBP officers working during screenings for the Ebola virus at John F. Kennedy International Airport in New York, New York, USA, 11 October 2014.  (US CBP / HANDOUT / EPA)

A woman reads a pamphlet as New York Healthcare workers attend an Ebola educational session at the Jacob Javits Convention center in New York, October 21, 2014.   (Mike Segar / Reuters)

Passengers disembark from the Carnival Magic cruise ship after it reached port in Galveston, Texas October 19, 2014. The Carnival Magic arrived on Sunday after a week-long trip with a Dallas hospital lab worker on board who spent much of the cruise in isolation after possible exposure to Ebola.   (Daniel Kramer / Reuters Photo)

The Carnival Magic cruise ship off Cozumel island in the Caribbean, Mexico, on Oct. 17, 2014.   (GUSTAVO VILLEGAS / EPA)

President Barack Obama talks to the press after meeting with his team coordinating the government’s Ebola response in the Oval Office of the White House in Washington, October 16, 2014.

President Obama asked former White House adviser Ron Klain to serve as Ebola “czar” on Friday, October 17.  (Andrew H. Walker / Getty Images)

Emergency vehicles are seen in a Pentagon parking lot after a woman who recently traveled to Africa vomited there, in Washington October 17, 2014.  (Kevin Lamarque / Reuters)

Emergency workers, a few in hazmat suits, conduct their work in a Pentagon parking lot after a woman who recently traveled to Africa vomited there, in Washington October 17, 2014.  (Kevin Lamarque / Reuters)

United States Marine Corps officers Col. Dave Lapan (L) and Lt. Col. Eric Dent leave a cordoned-off police area after an Ebola scare in Washington, October 17, 2014. Lapan and Dent were on a chartered bus that was going from the Pentagon to the Marine Barracks in Washington when a woman, who was not part of their group, boarded and later vomited.  (Gary Cameron / Reuters)

A chartered bus that was going from the Pentagon to the Marine Barracks receives a police escort in Washington October 17, 2014. The bus was at the Pentagon when a woman boarded and later vomited.   (Gary Cameron / Reuters)

Texas nurse Amber Vinson is helped up the steps of a waiting aircraft by personnel in this still image taken from video courtesy of NBC5- KXAS in Dallas, Texas October 15, 2014.   (NBC5-KXAS / Reuters)

Clinical Director of Texas Health Resources Dr. Daniel Varga stands ready to answer questions at a press conference at the Dallas County Commissioners Court on October 15, 2014 in Dallas, Texas.  (Stewart F. House / Getty Images)

Centers for Disease Control and Prevention Director Tom Frieden (L) and National Institute of Allergy and Infectious Disease Director Anthony Fauci testify before a House Energy and Commerce Oversight and Investigations Subcommittee hearing on the U.S. response to the Ebola crisis, in Washington October 16, 2014.   (Jonathan Ernst / Reuters)

Emergency vehicles escort an ambulance on the tarmac at Love Field Airport. The ambulance had reportedly delivered Amber Vinson, a health care worker, to an air ambulance.   (Stewart F. House / Getty Images)

A flyer notifying area residents that a person living in the area has been diagnosed with Ebola hangs on the door of an apartment at The Village Bend East complex on Oct. 15.  (Mike Stone / Getty Images)

Members of a cleaning company work on sanitizing the apartment where Ebola patient Thomas Eric Duncan was staying in Dallas.  (Joe Raedle / Getty Images)