There is an 18 percent chance that a case of the Ebola virus will reach the United States by the end of September, according to a study published on Tuesday in PLOS Currents: Outbreaks. 

Despite restrictions reducing travel in and out of the infected countries by 80 percent, the study, which analyzes global flight patterns, suggests that a case of Ebola in the U.S. is becoming increasingly harder to avoid. It also lists the chance of the virus reaching the United Kingdom between 25 and 28 percent. 

The analysis also warns that if the current West African outbreak is not contained the likelihood of the virus reaching Europe and the U.S. will "increase consistently." 

The study lists just a five percent chance of Ebola occurring in the U.S. today, suggesting that the disease is far from contained to countries in West Africa. According to numbers obtained by the World Health Organization, there have been an estimated 3,685 cases and 1,841 deaths from the virus since the outbreak began. 

Although two Americans — Dr. Kent Brantley and Nancy Writebol — have been treated for Ebola in the U.S., both of them contracted the disease while working in Liberia. Doctors suggested that better medical care contributed to their eventual recovery.

A third infected American working in Liberia,  Dr. Richard A. Sacra, is on his way to the U.S. for treatment.