A new descendant of the Omicron variant of covid, XBB1.5, with great contagion capacity, is spreading at full speed in some areas of the United States and already represents the majority of cases in a country where infections are on the rise , fueled by travel and gatherings this festive season.
According to data from the Centers for Disease Control (CDC), the XBB and XBB1.5 subvariants accounted for 44.1% of all covid cases in the United States in the week of December 31.
A week earlier, that proportion was 25.9%.
And in the week of December 15 it was around 10%.
"Our concern is how contagious it is" the new subvariant, declared in Geneva the epidemiologist and technical manager of the response against covid at the World Health Organization (WHO), Maria Van Kerkhove.
"It is the most transmissible subvariant that has been detected so far," she pointed out this week at a press conference.
And while there is no indication that it is more deadly or causes more serious infections, the speed with which it spreads worries scientists.
“The more this virus circulates, the more opportunities it has to mutate.”
A concern that is exacerbated when China, the most populous country in the world and affected by a gigantic wave of covid, is preparing to open its borders this weekend for the first time in almost three years, amid criticism from the WHO and governments from all over the world. the world about the lack of transparency of their data.
XBB1.5 has been detected in 29 countries worldwide.
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The increased transmissibility of XBB1.5 and its predecessor XBB is due to mutations in this specific strain of the virus, which allow it to adhere to human cells more easily and replicate rapidly.
In the United States, the combination of the new subvariant and the holiday season that began in late November with Thanksgiving has led to an increase in the number of cases and hospitalizations.
The average daily income in the week from December 29 to January 3 is 6,519, according to CDC data, while in the previous seven days it was 5,613.
The number of cases in the last week has stood at 470,699, while immediately before the festivities began in November they were below 300,000.
The new mutation was detected for the first time in October in New York and Connecticut, in the northeastern US. Currently, according to CDC data, XBB and XBB1.5 infections already account for 75% of cases in the New York region, which also includes the State of New Jersey, Puerto Rico and the Virgin Islands.
In the Connecticut region, which includes Massachusetts, New Hampshire, Maine, Vermont, and Rhode Island, the prevalence is 86.2%.
So far, there are no data that suggest that, despite its greater contagion capacity, infections by this subvariant may be more serious.
Experts have stressed that existing covid vaccines and treatments seem to maintain their ability to fight this type of virus.
Given the much higher level of immunity among the population against covid, a return to the crisis moments of the last three years is not anticipated.
Not even to the escalation experienced a year ago, when the Omicron variant began to spread across the planet.
Then, the world experienced 25 million daily positive cases, seven times more than today;
although far fewer tests are now performed, since the vast majority of cases are mild or asymptomatic.
More hospitalizations
In New York, one of the foci of the new subvariant, hospitalizations have increased.
According to its Department of Health, the current rate is 22.26 per 100,000 residents, the highest since February 2022. But it is difficult to attribute the rise to XBB1.5: respiratory diseases proliferate in this winter season.
Most of those admitted with covid in this State, 54.8%, were not hospitalized for the virus.
His symptoms were weak enough that the disease could only be detected by a test.
"We expect new waves of infection in the world, but that does not have to translate into new waves of death, because our measures against the virus continue to work," Van Kerkhove stressed at the press conference.
A WHO technical group on the evolution of the virus has begun an assessment to analyze the risk of the new subvariant, and is closely monitoring any possible changes in the severity of XBB and XBB1.5, using laboratory studies and data obtained among the population.
According to Van Kerkhove, the report is expected to be published in the coming days.
In the United States, the CDC has reiterated appeals to the population to receive the booster dose.
Although 70% of the country's inhabitants are vaccinated with two doses, only 15.4% of those over five years of age have received the booster dose.
A figure well below expectations when the new immunization campaign was launched in August.
Only among those over 65 years of age, the population at highest risk, rises to 38.1%.
The US government aspires to make covid vaccines an annual campaign, as one of those immunized with all doses, President Joe Biden, pointed out in October.
“For most Americans, one dose against covid a year will be all they need,” he declared at the time at an event at the White House.
“And if they receive it, they will be protected.
And if you don't, you are putting yourself and others at unnecessary risk.”
For now, Washington has renewed this week the order that requires a vaccination certificate for foreign visitors to the United States.
This Government will also require travelers from China to present a negative coronavirus test carried out no more than 48 hours before the flight time.
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