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When Houston was gripped by a severe Covid-19 wave in June, a mutated form of coronavirus that developed elsewhere in the world and which is known to be especially contagious grew to eventually dominate the city’s infected patients, according to a study released Wednesday that could raise new questions about how quickly the virus evolved as it spread around the world.
The study, which was not peer-reviewed and was first reported by the Washington Post, looked at virus samples from two different Covid-19 waves in the Houston area over the spring and summer.
- Many different strains of the virus entered Houston initially, but when the city moved from a small initial wave in March to a much larger outbreak in late June, almost every coronavirus sample contained a particular mutation on the virus’ surface that had previously been found in cases in Europe.
- Patients with that strain of coronavirus carried more virus particles than other people, meaning they were probably more infectious, the study found.
- Researchers say the rise of this contagious strain of the virus may have driven up the infection rate in the Houston area, which jumped from an average of around 200 new Covid-19 cases per day to more than 2,400.
- The mutation did not appear to make the virus more dangerous or change patients’ outcomes, according to the study.
- A similar study from earlier this month found evidence that the United Kingdom was also overtaken by the same virus strain over the spring.
Scientists are not surprised that coronavirus has evolved over time. Mutations take place when a virus replicates and, after infecting more than 30 million people, coronavirus has had plenty of opportunities to mutate. Most mutations have no impact, but this process sometimes changes the virus’ behavior or makeup, and if that change helps the virus spread, a mutated version of the virus can eventually dominate through natural selection. This study from Houston is the latest evidence that coronavirus is changing as it moves around, possibly becoming slightly more infectious in the process.
What to Watch For
If coronavirus is evolving over time, that process could impact the effectiveness of a vaccine. The virus rarely infects the same person twice, but some research shows that reinfection is more possible if a patient gets two different strains of coronavirus. For that reason, as the virus changes, a vaccine might need to change along with it.
“We’ll have to chase the virus and, as it mutates, we’ll have to tinker with our vaccine,” David Morens, a virologist and advisor at the National Institute of Allergy and Infectious Diseases, told the Washington Post.