Overestimated mutation rate

April 5, 2018 by Fabio Bergamin, ETH Zurich
The Ebola virus, isolated in November 2014 from patient blood samples obtained in Mali. The virus was isolated on Vero cells in a BSL-4 suite at Rocky Mountain Laboratories. Credit: NIAID

At the start of the epidemic in West Africa, the Ebola virus did not change as rapidly as thought at the time. ETH researchers explain why scientists misjudged it at the time.

Scientific evidence at the start of the last major Ebola in West Africa that suggested the would change exceptionally rapidly was probably due to methodological biases. This has been shown by scientists led by Tanja Stadler, a professor at ETH Zurich's Department of Biosystems Science and Engineering in Basel; they published the corresponding study in the journal PNAS this week.

When Ebola developed into an epidemic in 2014, an international team of scientists estimated that the pathogen's genome would change on average every 9.5 days, based on virus samples and computer simulations. This estimate is an atypically high rate of change. Normally, the Ebola virus genome only mutates at just under half that speed. The high mutation rate led to fears at the time that if the virus rapidly altered, it could also quickly become more virulent.

However, in later studies, researchers evaluating much larger numbers of virus samples could not confirm the high rate. They showed that when viewed over the whole epidemic, the pathogen only changed at its typical slow speed.

ETH researchers have now shown that the high estimated mutation rates at the start of the epidemic were due to the limited number of virus samples at the time in combination with the computer models used, which calculate the estimates using from and from underlying assumptions.

"The smaller the amount of genetic data available for a , the bigger the influence of the underlying model assumptions on the end result," explains ETH professor Stadler. She highlights that the early estimates for the Ebola epidemic based on a small dataset were heavily influenced by assumptions, which in retrospect have proven to be inaccurate.

Current computer models, however, do not simplify reality as much as those used a few years ago, and they are less heavily influenced by the underlying assumptions, says Stadler. For example, the new models no longer assume that everyone infected has the same probability of passing on the pathogen to other people; instead, they take into account different population structures. While the new models – some of which are being developed in the Stadler group – are more complex and require a lot more computation, they provide more accurate results even at the start of an epidemic, when very little genetic data is available. New calculations by the ETH scientists with the genetic data from 2014 show this increase in accuracy.

Explore further: The mathematics behind the Ebola epidemic

More information: Simon Möller et al. Impact of the tree prior on estimating clock rates during epidemic outbreaks, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1713314115

Related Stories

The mathematics behind the Ebola epidemic

October 9, 2014
Researchers in the Department of Biosystems Science and Engineering at ETH Zurich have calculated new benchmark figures to precisely describe the Ebola epidemic in West Africa from a mathematical perspective. Their results ...

New study eases fears of airborne Ebola

May 15, 2015
At the peak of the Ebola epidemic last fall came a frightening new possibility: a mutation that could allow the disease to spread through the air. Now University of Florida researchers have dispelled this concern using data ...

Responders to recent West Africa Ebola epidemic show little evidence of infection

May 16, 2017
Responders to the West African Ebola epidemic of 2014-2016 who returned to the UK and Ireland included many who reported possible Ebola virus exposure or Ebola-associated symptoms, according to a new study published in PLOS ...

Ebola virus infects reproductive organs in monkeys

February 8, 2018
Ebola virus can infect the reproductive organs of male and female macaques, according to a study published in The American Journal of Pathology, suggesting that humans could be similarly infected. Prior studies of survivors ...

Ebola virus has mutated less than scientists feared, study finds

March 26, 2015
The Ebola virus is not mutating as quickly as scientists had feared, which is good news for treating the disease and preventing its spread, a study showed Thursday.

Sierra Leone Ebola lockdown was too short: Swiss research

October 9, 2014
Three-day quarantines are not enough to net all Ebola cases in a given area, Swiss scientists said this week after using genetic sequencing to map the early spread of the virus in Sierra Leone.

Recommended for you

Drug targets for Ebola, Dengue, and Zika viruses found in lab study

December 13, 2018
No drugs are currently available to treat Ebola, Dengue, or Zika viruses, which infect millions of people every year and result in severe illness, birth defects, and even death. New research from the Gladstone Institutes ...

Faster test for Ebola shows promising results in field trials

December 13, 2018
A team of researchers with members from the U.S., Senegal and Guinea, in cooperation with Becton, Dickinson and Company (BD), has developed a faster test for the Ebola virus than those currently in use. In their paper published ...

Urbanisation and air travel leading to growing risk of pandemic

December 13, 2018
Increased arrivals by air and urbanisation are the two main factors leading to a growing vulnerability to pandemics in our cities, a University of Sydney research team has found.

Researchers discover new interactions between Ebola virus and human proteins

December 13, 2018
Several new connections have been discovered between the proteins of the Ebola virus and human host cells, a finding that provides insight on ways to prevent the deadly Ebola virus from reproducing and could lead to novel ...

Faecal transplants, 'robotic guts' and the fight against deadly gut bugs

December 13, 2018
A simple compound found in our gut could help to stop dangerous bacteria behind severe, and sometimes fatal, hospital infections.

Taking the virus out of a mosquito's bite

December 12, 2018
They approach with the telltale sign—a high-pitched whine. It's a warning that you are a mosquito's next meal. But that mosquito might carry a virus, and now the virus is in you. Now, with the help of state-of-the-art technology, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.