The coronavirus continues to impress with its rapid evolution.
Over the past few weeks, there has been a new version of XBB in the US. The CDC estimated that 72 percent of new cases in the Northeast were caused by the disease.
In New York State, the new subvariant has a potent array of mutations that appear to help it evade immune defences and improve its ability to invade cells.
The Covid-19 technical lead at the World Health Organization said at a news conference on Wednesday that it is the most transmissible variant that has been detected yet.
In most of the world, XBB. 1.5 is a rarity. He expects it to spread quickly and globally. He said that there would be another wave of infections.
Advisers at W.H.O. are looking at the risk that XBB. 1.5 poses. The surge in cases would not match the first Omicron spike that Americans experienced a year ago, according to Jacob Lemieux, an infectious disease doctor at Massachusetts General Hospital. He asked if it was a Category five storm. I don't think so.
He warned that a rough Covid winter could be made worse by the fact that people don't receive boosters that can ward off diseases.
The Biden administration is watching the emergence of XBB. 1.5 and is encouraging people to take advantage of existing countermeasures. Bivalent vaccines may provide decent protection against XBB. Paxlovid will help fight infections.
Dr. Jha said that they were pretty confident that the countermeasures would work. We have to make sure they are being used.
The experts are confident that XBB. 1.5 is not the end of the coronaviruses evolution. They expect that a descendant of XBB. 1.5 will be better at spreading.
It's possible that that descendant already exists and is infecting people. The discovery of the next generation of XBB. 1.5 may be delayed because of the decline in the number of sequencers. It is difficult for us to track each of the subvariants of Omicron because of the less and less availability of sequencing.
The evolution of XBB. 1.5 has been reconstructed by scientists using online databases. The first step was taken last year when two earlier forms of Omicron were found in the same person. The viruses' genetic material was shuffled. The hybrid form had genetic material from both parents. It was called XBB by virus watchers.
It happens a lot among coronaviruses. Scientists have found a number of different forms of the same disease.
In a matter of weeks or months, most of the SARS-coV-2 viruses have disappeared. The winner of the genetic lottery was XBB. From one parent, it gained a set of changes that made it resistant to previous infections. It was even more evasive because it gained a set of different genes from the other parent.
According to Thomas Peacock, a researcher at Imperial College London, XBB picked up the most possible genes from the parents. XBB was one of the most evasive Omicron subvariants last summer.
Experiments show that XBB paid a heavy price for its power. The shape of the spike that covers it's surface is altered by the changes. It's harder for XBB spike proteins to grab tightly to cells because of some of the changes that have been made.
XBB had an advantage against other forms of the virus. It was in close proximity to a number of other Omicron subvariants. In Singapore, XBB caused a surge in October, but is still rare in other parts of the world.
It continued to change into new forms. In October, the first samples of XBB. 1.5 were isolated. F486P was gained by the new sub variant.
XBB. 1.5 was compared against earlier forms of XBB by a group of people. The previous forms of XBB could still be evaded by the new sub variant.
They posted their results online. The data has not been published.
The northeastern United States is where early samples of XBB. 1.5 were first identified. Scientists were able to track its growth once they recognized it.
Nathan Grubaugh and his colleagues at Yale University found that by mid-December other Omicron subvariants were falling. The number of XBB. 1.5 cases was growing. It is 20 percent more transmissible than BQ.1, according to Dr. Grubaugh.
He said that it doesn't have the big waves we saw before. It won't be close to what it was last year.
It's not known how severe XBB. 1.5 infections are compared to other coronaviruses. The doctor said it was serious. I don't know if it's more serious than other Omicrons in terms of the impact.
XBB. 1.5 has spread to other countries and is growing fast in Germany. It's impact is likely to be different in different places. It may face stronger immunity in India due to the number of people who were exposed to it last year.
In China, which experienced a large surge of cases late in the year, its prospects are even more difficult to predict. Most of the time, China didn't share virus sequence with international databases. The state of play in the country is not reflected in the databases.
XBB. 1.5 has an advantage in the United States due to its ability to evade immunity. There is less immunity in China. After other variant spread through China, it may be XBB. 1.5's turn to rise.
He wasn't sure if restrictions on Chinese travelers would keep cases down. He thought it was pointless. The elderly should be well-vaccinated.
Experts think that XBB. 1.5 can become even better at evading antibodies as it continues to evolve.
The scientists are trying to find an upgraded version of XBB. Governments are pulling back on efforts to sequence things. Dr. Peacock said that the world has taken a hit on the project.
The United States has been able to maintain a strong effort. XBB. 1.5 could have stayed under the radar for a long time without it. The next generation of XBB. 1.5 may not be known for some time.
Dr. Lemieux said that it was a mistake to cut back on the number of tests done. He said it's a part of public health.
According to Dr. Peacock, the evolution of the coronaviruses would not slow down. He suggested that we should give it another two years and see where we are.
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