Five questions about delta variants


In the past two weeks, the number of Covid cases in the United States has doubled, and scientists are now racing to understand the delta variant, which seems to be responsible for the vast majority of new infections. Disturbingly, delta is more contagious than other variants, and it has also caused some symptomatic “breakthrough” cases in the vaccinated population.

Although vaccines can still prevent serious illness and death in an overwhelming way, delta variants have changed our perception of the spread of coronavirus. Here are answers to some important questions about what all this means.

1. What makes delta variants more contagious?

according to CDC estimates, The delta variant is almost twice as infectious as the previous version of the virus. Researchers are still trying to understand The mutation that explains this, but preliminary studies have shown that changes in its spike protein make it more effective at grasping receptors and entering cells.

The delta variant also seems to cause a higher viral load than the other variants. Viral load is a measure of how much virus is in your nose and throat. A study It was found that at the beginning of the infection, the viral load of the person with the delta variant was 1,000 times that of the person infected with the original version of the virus. According to this study, which has not been peer-reviewed, people with delta variants can also reach peak viral load faster.

2. How do scientists actually measure the infectivity of delta variants?

The viral load helps us understand how infectious the virus is. When an infected person coughs, sneezes, or just breathes, the coronavirus infection is spread through aerosols and droplets-therefore, the more virus particles in a person’s respiratory tract, the more likely that person will infect other people.

To measure viral load, researchers use a laboratory method called polymerase chain reaction or PCR. They wipe the nose of the infected person and extract any viral RNA on the swab. Next, they run a reaction, looking for genetic material from the virus and copying it over and over again, until there are enough copies for laboratory equipment to test.

We usually focus on the final stage of PCR-testing whether material is found in the virus, which will produce a positive result. But researchers can also see how long it takes for the machine to return a positive result—how many copies are needed for the viral material to reach a detectable level. The fewer copies or cycles required to detect the virus, the more viral material is required to start.

This number of cycles (called Cycle Threshold or Ct) is a number that is of concern to the Centers for Disease Control and a Provincetown case clusterIn Massachusetts, approximately 74% of state residents participated in vaccination. Whether vaccinated or not, infected people often have similar Ct values. CDC believes this may indicate People who are vaccinated may spread the virus, Maybe as easy as an unvaccinated person.

3. Even if I am vaccinated, will I still be infected with the new coronavirus?

Yes, it is possible, although your infection may be much more serious than an unvaccinated person.

The vast majority of infected people are still unvaccinated people, saying Liz Rogowski McQuade, An infectious disease researcher at the University of Virginia.According to reports Caesars Family Foundation, US states that track vaccination status of cases found that 94% to 99.9% of cases occurred in unvaccinated people. Among everyone who has been vaccinated, 0.01% to 0.54% have experienced breakthrough cases.

Some learn Vaccines have been found to be slightly less effective against delta variants, especially if you only have one dose of mRNA vaccine.But so far it looks like Vaccines are still effective to a large extentRogawski McQuade said, especially in the prevention of many severe cases.

Vaccines may eventually need some additional help to combat delta variants-some companies are Boost booster shootingBut experts say that there is no evidence that boosters are necessary, and WHO maintains Initial vaccines in other parts of the world should be given priority over boosted injections by people in rich countries.

4. What about transmission? Can vaccinated people transmit delta variants?

It seems so, but research is still in its early stages.

Although the Ct value can be used as a surrogate value for the viral load, there are some problems with trying too many hypotheses based on this figure, especially in the vaccinated population, according to Monica Gandhi, An infectious disease researcher at the University of California, San Francisco.

First, PCR can collect all kinds of genetic material, even genetic material from dead viruses. If your vaccinated immune system has begun to fight the infection, “you may have a lot of virus particles in your nose, but they may not work,” Gandhi said. In order to truly understand someone’s infectiousness, you need to carry these viruses to see if they are still alive and capable of infecting people. Gandhi said that the CDC pointed out that these data are still pending.


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