But these three versions of the virus are just a few among thousands of SARS-CoV-2 variants that have sprung up since the pandemic began. Many of these variants have since vanished. So why do some versions disappear, and why does the virus change in the first place? What mechanisms play puppet master for evolving viruses? A successful virus is one that makes more of itself. In order to replicate, they must find a host. The majority of mutations are harmful to a virus or cell, limiting the spread of an error through a population.
Many other mutations are neutral, having no effect on how efficiently a virus or cell reproduces. However, a select few mutations prove useful to a virus or cell. For example, some changes could make a virus better at jumping from one host to the next, helping it outcompete other variants in the area. Scientists estimate the variant is roughly 50 percent more transmissible than past forms of the virus, giving it an evolutionary edge. Mutations may happen randomly, but the rate at which they occur depends on the virus.
The enzymes that copy DNA viruses, called DNA polymerases, can proofread and fix errors in the resulting strings of genetic letters, leaving few mutations in each generation of copies. Coronaviruses have a slightly lower mutation rate than many other RNA viruses because they can do some light genetic proofreading. So as the novel coronavirus ran amok around the world, it was inevitable that a range of variants would arise. The true mutation rate of a virus is difficult to measure though.
Unlike mutation rate, this is measured over a period of time. So the more a virus spreads, the more opportunities it has to replicate, the higher its fixation rate will be, and the more the virus will evolve, Duffy says. But this process may not always happen at a steady pace. In December , the variant B. Some scientists speculate that a chronically ill patient provided more opportunities for replication and mutation , and the use of therapies such as convalescent plasma may have pressured the virus to evolve.
Not every change was necessarily useful to the virus, Duffy notes, yet some mutations that emerged allowed the variant to spread rapidly. Mutations drive evolution, but they are not the only way that a virus can change over time. Some viruses, like influenza, have other ways to increase their diversity. Once a virus is circulating among human beings, their environment is us.
That means that every random mutation that viruses make is another chance that they could better adapt to us. And the ones with the most adaptive features will survive and multiply. That's why some viruses, like Swine flu, have gotten more dangerous over time and developed the ability to jump from person to person.
But then again, this doesn't always happen — it's a game of chance. Some viruses that people are watching closely for some time haven 't developed this ability.
H5N1 avian flu is still in this category, and let's hope it stays that way. Adaptation to people is one reason why controlling emerging infectious diseases like swine flu and MERS is so important. The longer they circulate among people, the longer they have to evolve adaptations that are more advantageous to them — and more dangerous to us. Bacteria multiply quickly, but not as quickly as some viruses, as you can see from this chart. Streptococcus bacteria include things like pneumonia. Here, too, there's a lot of variation.
For example, a population of E. But there's a twist: When we start overusing antibiotics to kill bacteria, that can actually speed up the process of evolution. When people overuse and misuse antibiotic drugs, they kill off bacteria that are susceptible to the drugs while leaving the stronger ones behind.
Then those grow and multiply. Essentially, we are making bacteria evolve to become deadlier and more difficult to treat. In other words, it's not them, it's us. These specially evolved bacteria are becoming a huge problem. Antibiotic-resistant infections currently kill 23, Americans each year. And new drugs to replace them aren't coming out like they used to either. The World Health Organization warned that we could be headed for a post-antibiotic era unless things shape up fast.
Our mission has never been more vital than it is in this moment: to empower through understanding. What is a coronavirus? The pandemic virus is slowly mutating. But is it getting more dangerous? Challenge 2: How does a virus enter a host? Challenge 3: Molecular Hijacking: How does a virus take over? Challenge 4: How do mutations cause viral evolution? Your browser is antiquated and no longer supported on this website.
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