Four people in Oregon are being monitored by the Oregon Health Authority for possible exposure to the deadly Ebola virus, state officials said Thursday morning.

The four — whose identities, nationalities or current locations have not been disclosed — have not tested positive for the virus or shown symptoms, said Dr. Richard Leman, an infectious disease expert with the Oregon Health Authority.

“There is low risk for people in Oregon,” OHA said in a statement.

OHA said it is following a public health protocol to inform state residents when someone who has been in an area with a outbreak of a major virus come to or return to Oregon. 

While both Ebola and COVID-19 are viral infections, they differ in how they spread and their deadliness.

COVID-19 can be spread rapidly spread through droplets in the breath of an infected person. The World Health Organization reports COVID-19 has a worldwide mortality rate of about 3.4% of all those infected. The nearly 2.75 million COVID-19 deaths worldwide are because of the rapid spread that has caused 125 million infections on every continent.

Ebola is spread through blood or body fluids of an infected person exhibiting symptoms. That limits the spread of the virus, but it is far deadlier — an estimated 50% of those infected die.

Medical workers and staff treating those with Ebola are at a particularly at risk and can become ill from patients, as well as from the vomit, feces or belongings of those infected.

Ebola can be spread through sex with an infected person. Infections have also been reported during the handling of Ebola victims’ corpses for burial and transmission through the breast milk of infected mothers.

Unlike COVID-19, someone who is asymptomatic of Ebola cannot spread the Ebola virus.

Treatments and a vaccine for Ebola were approved in 2020 by the U.S. Food and Drug Administration. Outbreaks occur in areas where vaccination levels are low.

Leman said health authorities need to balance the level of possible threat to the general public vs. the privacy of the individual who has been in an outbreak zone but not shown any symptoms.

Releasing more information could generate unfounded fears about the person or their location, which Lehman said would keep people from self-reporting their presence in the regions and staying in touch with public health authorities.

“It’s really a double-edged sword,” Leman said. 

Oregon has gone through the Ebola reporting protocols in 2014, 2015 and 2019, Lehman said. No one in Oregon has become infected with Ebola during the prior periods. 

The current alert came after the U.S. Centers for Disease Control announced a new outbreak.

The Democratic Republic of the Congo on Feb. 7 reported an outbreak in Butembo, in North Kivu province.  Latest reports show 12 people have become infected and six have died. Formerly known as Zaire, the DRC is the largest country in sub-Saharan Africa. It’s population is 87 million.

The British medical journal, The Lancet, reported an outbreak on Feb. 14 in N’Zérékoré Prefecture in the southeast of the West African country of Guinea, with 18 Ebola cases and nine deaths in recent weeks. Guinea has a population of 12.4 million.

“The outbreaks are limited to small areas of each country and are not in the large population centers,” OHA said in its statement.

Both countries have been the center of earlier outbreaks of Ebola.

Lehman said people who travel between Oregon and the two countries could include medical teams going to Africa to aid in disease prevention, religious missionaries, visitors from the countries or residents of Oregon who are from the countries and are returning home.

Though OHA would not say where in Oregon the people are currently located, their whereabouts are known and local public health officials are being included in potential response or care.

Lehman said Ebola usually has an incubation period of between two and 21 days and that the four being monitored are believed to be near the end of that period. 

When symptoms do arise, they come on rapidly.

“It hits you like a ton of bricks,” Leman said. “A fever, very high, muscle aches, and chills.”

Other symptoms can include unexplained bruising and bleeding and diarrhea. 

The virus was first isolated in 1976 during two outbreaks, one in South Sudan and another in the village of Yambuku in the Democratic Republic of Congo. The village sits beside the Ebola River, from which the disease takes its name.

Researchers believe the initial cases were infections that transferred from fruit bats and other animals to humans, after which the virus mutated to enable human-to-human transmission.

West African nations reported outbreaks in 1978 and 1979, then no reported cases again until 1994. Another lull began in 1997, but since 2000, there have been 32 distinct outbreaks.

The 2014–2016 outbreak was rated an epidemic by the World Health Organization. It recorded 28,616 cases and 11,323 deaths in Guinea, Liberia, and Sierra Leone. The outbreak spread to more than a dozen other countries in western and southern Africa.

During the epidemic, 11 cases and one death were reported by the CDC in the United States. Almost all were medical patients evacuated from Africa or airline passengers who became ill and were hospitalized upon arrival. Two nurses in the United States working with Ebola patients became infected, but both survived.

One healthcare worker each from the United Kingdom, Italy and Spain were infected while treating Ebola patients. All survived. A researcher in Russia working on a vaccine was mistakenly injected with Ebola and died.