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Concerns about the Ebola virus were heightened Sunday when a health care worker in Texas had a positive preliminary test for the disease. The worker’s case marks the first known transmission of Ebola in the United States and the second diagnosis in the country.

With developments pouring in from all corners of the world, here’s what you need to know to quickly get caught up:

U.S. CASES

New case in Texas:

A person who helped to treat Thomas Eric Duncan may be the first person to contract the disease while in the United States. The health care worker from Texas Health Presbyterian Hospital tested positive in a preliminary test Saturday after reporting a low-grade fever Friday. The CDC is working to confirm the diagnosis.

CDC head says protocols work:

Dr. Tom Frieden, the director of the CDC, told reporters Sunday that the health care worker who appears to have contracted in Ebola was infected because of a breach in protocols.

He mentioned that one of the times that people working in protective clothing are at risk is when they are taking off their gear, but he said CDC investigators are working to determine what happened. “The protocols work. … But we know that even a single lapse or breach can result in infection,” he said.

NBC cameraman’s condition improving:

Doctors at a Nebraska hospital are pleased with the progress being made by NBC cameraman Ashoka Mukpo, who contracted Ebola while working in Liberia.

Mukpo, an American citizen, is receiving an experimental drug called brincidofovir, or CMX001.

“With the Ebola virus, you never relax completely, but we think he has made great progress,” said Dr. Phil Smith with The Nebraska Medical Center, where Mukpo is being treated.

Earlier, Smith had said that Mukpo’s condition had “slightly improved.”

“He’s been taking in some fluids and drinking Gatorade. But everyone needs to be reminded that this is still a very serious illness we’re dealing with and no one has a lot of experience treating it,” Smith said.

Massachusetts patient exhibits possible Ebola symptoms:

A patient who has been to Liberia presented himself Sunday at a medical center in Braintree, Massachusetts, complaining of headache and muscle aches.

“Out of an abundance of caution, we immediately notified authorities and the patient was securely removed from the building and put into an ambulance now headed to Beth Israel Deaconess Medical Center. The building was closed briefly but has now reopened,” Ben Kruskal, chief of infectious disease at Harvard Vanguard Medical Associates, said in a statement.

New travel screening:

Five of America’s biggest, busiest airports are beefing up measures. On Saturday, people arriving from the three nations hardest hit by Ebola started getting special screening, including having their temperature taken, at New York’s JFK airport.

“That screening went smoothly,” Frieden said Sunday. “There are a lot of lessons being learned through that to make sure that screening goes smoothly for passengers, other passengers.”

Washington’s Dulles, Newark, Chicago’s O’Hare and Atlanta international airports will begin screening Thursday.

WEST AFRICA

No relief in sight:

The number of deaths attributed to the current Ebola outbreak has climbed to 4,033, the World Health Organization reported Friday. The tally brings the total number of confirmed, probable and suspected cases of Ebola to 8,399. The numbers were reported from Guinea, Liberia, Nigeria, Senegal, Sierra Leone, Spain and the United States.

U.S. troops arrive in Liberia:

A group of 90 U.S. Marines and airmen arrived in Liberia on Thursday to help Ebola response efforts, along with four V-22 Osprey aircraft and two C-130 transport planes.

Their arrival brings the total number of U.S. troops deployed in Liberia to 334, military spokesman Lt. Col. Dave Doherty said. There are more coming. In late October, 700 troops from the 101st Airborne Division are scheduled to deploy to Liberia.

IN OTHER COUNTRIES

Spain Ebola patient has no significant change in condition:

Teresa Romero Ramos, a nurse’s assistant in Spain who is the first person to contract Ebola outside Africa, “is conscious and talking” but was in “stable but serious” condition Saturday after taking a turn for the worse earlier in the week.

She has been treated with the anti-influenza drug Avigan, hospital sources with knowledge of the case said.

Sporadic infections unavoidable, the WHO says:

Sporadic Ebola infections will be unavoidable in some European countries because of direct travel from their hubs to hotspot areas in West Africa, the World Health Organization said Wednesday. But the risk of spread, it said, is avoidable and extremely low.

United Kingdom:

The UK’s Heathrow and Gatwick airports and Eurostar railway terminals will begin screening passengers arriving from Ebola-affected Liberia, Sierra Leone and Guinea, a government spokesman said.

Screening will involve assessing passengers’ recent travel history, who they have been in contact with and future travel arrangements, as well as a possible assessment performed by medical personnel.