The Ebola outbreak in West Africa has already killed 600 people. The outbreak occurred this spring, but a new study shows that the virus may have been affecting people in the region for years before the outbreak.

According to the study, there was a mysterious illness affecting people in West Africa years before the outbreak. The illness was likely the Ebola virus. Although blood samples were taken from most of the people treated for the illness, none of them were tested for Ebola.

Researchers are now testing the blood samples to see if the patients were indeed suffering from the Ebola virus. The test samples were over seven years old, but still potentially dangerous. Researchers had to heat treat them to help make them safe before they could be tested.

“It had been circulating there for a long time,” said Randal Schoepp of the U.S. Army Medical Research Institute of Infectious Diseases. “It just hadn’t gotten out of control or the right conditions weren’t there.”

Ebola virus that’s killed at least 600 in West Africa may have been smoldering there for years http://t.co/7EB1LFKiJo pic.twitter.com/gwopdsPY0X

— NBC News (@NBCNews) July 20, 2014

Researchers admitted that the tests are not 100 percent accurate, but they also believe that the outbreak did not just come out of nowhere. Viruses like Ebola travel from one host to the next and can be carried by animals like bats, monkeys and rodents.

“It makes us realize that you don’t have to see an outbreak (to know a virus is circulating in an area),” Schoepp said. “In Africa, it is easy for a disease to smolder because there is so much disease.”

While Ebola is common in some parts of Africa, it has never been seen before in West Africa. There are many other viruses that are common in the region, including Lassa Fever and Malaria.

It's important to bury dead bodies safely so they don’t pose health risk 2 other people http://t.co/mOEEVIbh2A #Ebola pic.twitter.com/kLMtUOLtfi

— WHO (@WHO) July 21, 2014

Both of these diseases are nasty and can spread easily. Lassa Fever symptoms are very similar to Ebola symptoms, but the viruses are unrelated.

Researchers believe that many Ebola cases were misidentified as Lassa Fever before the outbreak.

Do you think the Ebola virus was making people sick in West Africa long before the 2014 outbreak?

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