COVID-19 updates: Elizabeth Warren tests positive
The senator says she's experiencing "mild symptoms."
As the COVID-19 pandemic has swept the globe, more than 5.3 million people have died from the disease worldwide, including over 806,000 Americans, according to real-time data compiled by Johns Hopkins University's Center for Systems Science and Engineering.
About 61.4% of the population in the United States is fully vaccinated against COVID-19, according to data from the Centers for Disease Control and Prevention.
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Cornell moves exams online due to 'substantial' number of suspected omicron cases
Cornell University is moving into a "level red" alert after a "significant" number of suspected omicron cases were detected among student samples.
"While we must await confirmatory sequencing information to be sure that the source is Omicron, we are proceeding as if it is," university president Martha Pollack wrote in a letter to the community.
All final exams will be online beginning Tuesday, Pollack announced, and libraries and fitness centers are closed.
All undergraduate events are canceled, as is Saturday's recognition ceremony for December graduates, Pollack said.
Cornell has recorded more than 600 confirmed cases among students and staff in the last week alone, according to the university dashboard. While no infected students are seriously sick, Pollack said the university has "a role to play in reducing the spread."
-ABC News' Arielle Mitropoulos, Chris Donato
Omicron 'spreading at a rate we have not seen,' WHO says
"Omicron is spreading at a rate we have not seen with any previous variant," World Health Organization Director-General Dr. Tedros Adhanom Ghebreyesus warned Tuesday.
Omicron has been reported in 77 countries, he said, adding that the new variant is likely in most countries.
Tedros said health officials are "concerned that people are dismissing omicron as mild."
"Even if omicron does cause less severe disease, the sheer number of cases could once again overwhelm unprepared health systems," he said.
-ABC News' Christine Theodorou
England to lift travel ban on southern African nations
British Transport Secretary Grant Schapps announced Tuesday that England will remove all southern African nations from its travel red list.
After the omicron variant was first discovered in South Africa and Botswana in November, several countries around the world, including England and the United States, imposed travel bans on a swath of nations in southern Africa.
The World Health Organization warned that blanket travel bans will not prevent the international spread of omicron, deemed a "variant of concern," and that restrictions place a heavy burden on lives and livelihoods.
The countries of Angola, Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia, Nigeria, South Africa, Zambia and Zimbabwe will be taken off England's travel red list on Wednesday at 4 a.m. GMT, according to Schapps, who noted that all current testing measures remain in place.
"As always, we keep all our travel measures under review and we may impose new restrictions should there be a need to do so to protect public health," Schapps wrote on Twitter Tuesday.
Despite the travel bans, the heavily mutated variant has taken a foothold in London. British Health Secretary Sajid Javid told Parliament on Monday that omicron accounts for more than 44% of COVID-19 infections in the U.K. capital and it's expected to become the dominant variant there by Wednesday, overtaking the highly contagious delta variant.
Addressing Parliament again on Tuesday, the health secretary called omicron "a grave threat" and said the "race" to get as many people vaccinated and boosted "is new national mission."
"Scientists have never seen a COVID-19 variant that’s capable of spreading so rapidly," Javid said.
-ABC News' Christine Theodorou
Proportion of omicron cases growing in US, CDC data show
The proportion of new cases of the omicron variant in the United States is steadily growing, according to new data released Tuesday by the Centers for Disease Control and Prevention.
The data show that omicron now accounts for 3% of all new COVID-19 cases nationwide, just over two weeks after it was first detected in the U.S. Last week, omicron was estimated to account for just 0.4% of all new cases nationwide. Epidemiologists, including Dr. John Brownstein, an ABC News contributor, cautioned that these figures are rough estimates.
Currently, the delta variant still accounts for the vast majority -- nearly 97% -- of new cases in the U.S., according to the CDC. More than half the country -- at least 34 states and Washington, D.C. -- have reported cases of the newly discovered variant.
-ABC News' Arielle Mitropoulos
Omicron appears to spread faster and vaccine less effective against it, WHO says
The omicron variant appears to have a "growth advantage" over the delta variant, the World Health Organization said in a technical brief released Sunday.
"It is spreading faster than the delta variant in South Africa where delta circulation was low, but also appears to spread more quickly than the delta variant in other countries where the incidence of delta is high, such as in the United Kingdom," the WHO said in the brief, which was dated Friday. "Whether omicron's observed rapid growth rate in countries with high levels of population immunity is related to immune evasion, intrinsic increased transmissibility, or a combination of both remains uncertain. However, given the current available data, it is likely that omicron will outpace the delta variant where community transmission occurs."
Meanwhile, preliminary findings from South Africa suggest omicron may cause less severe illness than delta, and all cases of omicron reported in Europe to date have been mild or asymptomatic. But the WHO said "it remains unclear to what extent omicron may be inherently less virulent" and that "more data are needed to understand the severity profile."
The WHO also noted that "there are limited available data, and no peer-reviewed evidence, on vaccine efficacy or effectiveness to date for omicron." However, preliminary evidence, and the considerably altered antigenic profile of the variant's spike protein, suggests a reduction in vaccine efficacy against infection and transmission associated with omicron.
"There is some preliminary evidence that the incidence of reinfection has increased in South Africa, which may be associated with humoral (antibody-mediated) immune evasion," the WHO said.
The diagnostic accuracy of routinely used polymerase chain reaction (PCR) test and antigen-based rapid diagnostic test (Ag-RDT) assays does not appear to be influenced by omicron. Therapeutic interventions for the management of severe or critical COVID-19 symptoms associated with omicron are also expected to remain effective, according to the WHO.
"However, monoclonal antibodies will need to be tested individually, for their antigen binding and virus neutralization and these studies should be prioritized," the WHO added.
-ABC News' Christine Theodorou