Based on current evidence, scientists believe the Ebola virus, seen here in a colorized transmission electron micrograph, originates in animals (zoonotic).
With the largest Ebola outbreak in history raging through West Africa, understanding whether the virus is changing as it spreads through different populations can help responders know what treatments to use and also help research laboratories develop new tools to speed diagnosis in the field.
CDC scientists had access to genetic sequences from Guinea and Sierra Leone that had been published by other scientists. But the return to the United States of two American patients with Ebola infection underscored that no genetic sequences existed of the Liberian virus. The first patient was admitted to an Atlanta area hospital on August 3; CDC received samples on August 6. Scientists immediately applied diagnostic tests and also began the process of sequencing the genetic material in the samples.
Less than 72 hours after the first samples arrived, scientists had not only initial test results confirming that the patients were, indeed, infected with Ebola, but also the first detailed genetic sequencing of the Liberian virus. The genetic sequence information confirmed the Liberian viral samples were 99% identical to the virus circulating in Guinea and Sierra Leone. As important, CDC could see that the virus in the 2014 epidemic is 97% similar to the virus that first emerged in 1976.
Advanced molecular detection methods (AMD), like next generation sequencing, can show exactly where mutations are occurring in a pathogen. But in an outbreak, it is equally important to know if no mutations are occurring. This information helps doctors in the field have confidence in the treatments and interventions they’re using.
“Our aim is to design better tools to diagnose this illness. As a virus mutates, it can change in such a way that existing tests no longer pick it up. Thankfully, these data seem to indicate the virus is not changing in this outbreak,” said one of the CDC laboratory scientists.
With further analysis of additional samples from the American patients, CDC scientists will look to see if any other factors—such as other simultaneous infections—contributed to the severity of the illness. “We couldn’t do that before AMD technology,” scientists said.