Comparative Whole-ORF Evolutionary Analysis of the Seven Canonical Proteins of Bundibugyo Ebolavirus Across the 2007, 2012, and 2026 Outbreaks

Viruses are constantly changing. As they copy their genetic instructions to make new copies of themselves, small errors slip in, altering the proteins that make up the virus. For scientists studying dangerous pathogens like Ebola, tracking these changes is a matter of life and death. The virus is not a single, static object but a shifting collection of genetic code that evolves over time. When a virus jumps from one outbreak to another, or spreads across different regions, these tiny genetic shifts can accumulate. Some changes might help the virus hide from the immune system, while others might make it harder to treat. To understand how a virus behaves, researchers must look at its entire genetic blueprint, not just one small piece. This is particularly important for the Bundibugyo ebolavirus, a specific type of Ebola virus first discovered in Uganda in 2007. Since then, it has caused separate outbreaks in different parts of Africa, offering a rare chance to watch how the virus changes over nearly two decades.

A new study by Young-Chul Park at HTC Research takes a comprehensive look at how this virus has evolved across three distinct outbreaks: one in Uganda in 2007, another in the Democratic Republic of the Congo in 2012, and a third involving both countries in 2026. Instead of focusing on just one part of the virus, as many previous studies have done, this research examined all seven major proteins that make up the Bundibugyo ebolavirus. These proteins are the molecular machines that allow the virus to enter cells, copy its genetic material, and spread. By comparing the genetic sequences of 63 different virus samples from these three time periods, the researcher mapped out exactly where and how the virus changed. The goal was to see if the changes happened evenly across the virus or if certain parts changed more than others, and to understand the patterns of these changes over time.

The analysis revealed that the virus does not change in a uniform way. Some parts of the virus remain almost exactly the same, while others are constantly shifting. The most dramatic changes were found in two specific proteins: the glycoprotein, which sits on the surface of the virus and helps it attach to human cells, and the L protein, which acts as the engine for copying the virus's genetic code. The surface protein showed a wide variety of changes, but these were not scattered randomly. Instead, the changes were concentrated in specific sections of the protein that interact with the host cell, while other parts of the same protein remained very stable. This suggests that the virus is fine-tuning its ability to enter cells while keeping other essential functions steady. The L protein, which is the largest of the seven, contained the highest number of changes overall, spread out across its entire length. This indicates that the machinery responsible for copying the virus is also evolving, though in a more scattered pattern than the surface protein.

Other parts of the virus told a different story. The nucleoprotein, which wraps around the viral genetic material, showed a mix of changes, including some that appeared in one outbreak and stayed, and others that seemed to flip back and forth between different forms. In contrast, three other proteins—VP35, VP30, and VP24—showed very little change at all. These proteins are involved in the virus's internal operations, such as blocking the human immune system or helping the virus assemble. Their stability suggests that they are under strict pressure to remain unchanged; if they were to change too much, the virus might stop working. The fourth protein, VP40, behaved differently again. It showed changes, but these were mostly temporary variations that appeared within a single outbreak and did not persist into the next one. This means that while the virus might show some diversity in this protein during a specific event, it does not lock in those changes for the long term.

The study also classified these changes based on how they appeared over the nineteen-year span between the first and last outbreaks. Some changes became permanent, appearing in the 2012 samples and staying through 2026. Others were new discoveries in the 2026 samples that had never been seen before. A few changes even seemed to reverse, where the virus returned to a form it had in the earliest outbreak after changing in the middle. The researchers found that no single pattern explained the evolution of the entire virus. Instead, each of the seven proteins followed its own unique timeline. The surface protein and the copying engine were the most active, while the internal structural proteins remained largely frozen in time.

This work provides a detailed map of the virus's history, showing that evolution is not a single process but a collection of different processes happening at different speeds in different parts of the virus. By looking at the whole picture rather than just the surface, the study offers a clearer reference for scientists who track these viruses in the future. It establishes a baseline for what changes are normal and which parts of the virus are likely to stay the same. This kind of knowledge is crucial for genomic surveillance, helping public health officials understand if a new outbreak is a continuation of an old one or a fresh introduction. While the study does not test whether these changes make the virus more dangerous or harder to treat, it lays the groundwork for those future questions by defining exactly how the virus has changed over time. The result is a comprehensive view of a virus in motion, revealing that even within a single species, different parts of the genome can tell very different stories about survival and adaptation.