Live coverage has ended, please click here for NBC News' latest coverage of Covid-19.
The U.K. variant of Covid-19, which scientists say spreads more easily, has been detected across the U.S., including Texas, Connecticut and Pennsylvania.
That news came as the U.S. marked 4,000 deaths Thursday, according to an NBC News tally — the highest national daily total since the pandemic began.
Secretary of Health and Human Services Alex Azar said Wednesday that he is advising states to begin vaccinating lower-priority groups against Covid-19 if the doses they have on hand would otherwise be sitting in freezers.
- Map of U.S. hot spots and worldwide Covid-19 cases.
- Tracking surges in states across the country this winter.
- Map of travel restrictions and which states have a mask mandate.
- Click here for more of NBC News' Covid-19 coverage.
More than half of Covid spread comes from people without symptoms
Nearly 60 percent of all Covid-19 spread may come from people with no symptoms, according to a report from the Centers for Disease Control and Prevention published Thursday in the journal JAMA Network Open.
Using mathematical modeling, CDC researchers estimated that 35 percent of Covid-19 spread is from people who are contagious before they develop symptoms, called presymptomatic transmission. Another 24 percent comes from people who are truly asymptomatic, and never go on to develop symptoms.
Such widespread asymptomatic transmission means that simply identifying and isolating people who have symptoms of Covid-19 "will not control the ongoing spread of SARS-CoV-2," the virus that causes Covid-19, the study authors wrote.
Rather, the findings mean that everyday behaviors to mitigate the spread of the virus are even more critical.
"Measures such as wearing masks, hand hygiene, social distancing and strategic testing of people who are not ill will be foundational to slowing the spread," the study authors wrote, "until safe and effective vaccines are available and widely used."
Oxygen is the latest Covid bottleneck as hospitals cope with intense demand
As Los Angeles hospitals give record numbers of Covid patients oxygen, the systems and equipment needed to deliver the life-sustaining gas are faltering.
It’s gotten so bad that Los Angeles County officials are warning paramedics to conserve it. Some hospitals are having to delay releasing patients as they don’t have enough oxygen equipment to send home with them.
“Everybody is worried about what’s going to happen in the next week or so,” said Cathy Chidester, director of the L.A. County Emergency Medical Services Agency.
Oxygen, which makes up 21 percent of the Earth’s air, isn’t running short. But Covid damages the lungs, and the crush of patients in hot spots such as Los Angeles, the Navajo Nation, El Paso, Texas, and in New York last spring have needed high concentrations of it. That has stressed the infrastructure for delivering the gas to hospitals and their patients.
First case of Covid-19 variant confirmed in Pennsylvania
A case of the Covid-19 strain that was first reported in the United Kingdom in December has been confirmed in Pennsylvania, according to the state's Secretary of Health Dr. Rachel Levine.
Levine confirmed the case, in Dauphin County, on Thursday in a press release.
The person who tested positive, who has not been identified, did so after "known international exposure," according to the release. The state investigated the case and performed contact tracing in order to inform others who may have been exposed. The person who tested positive had mild symptoms but has since recovered.
“Pennsylvania has been preparing for this variant by working closely with the Centers for Disease Control and Prevention (CDC) and has been sending 10-35 random samples biweekly to the CDC since November to study sequencing and detect any potential cases for this new COVID-19 variant,” Dr. Levine said.
Virus mutation is common, according to the release, and while this particular strain is thought to spread more easily, there's no evidence the strain makes people sicker than the regular Covid-19 virus.
“There is still much to learn about this new variant, so we need to remain vigilant and continue to urge Pennsylvanians to stop the spread by washing their hands, practicing social distancing, avoiding gatherings, downloading COVID Alert PA and answering the call. Stay calm, stay alert and stay safe,” Dr. Levine said.
The newly discovered coronavirus variant has had confirmed cases in more than a dozen countries and at least four other states, including New York, California, Colorado and Florida.
Weekly initial jobless claims total 787,000
After a brief reprieve due to seasonal hiring, the latest weekly initial jobless claims total 787,000, according to data released Thursday by the Department of Labor. Analysts had predicted claims for the week ending Jan. 2 would total 803,000.
“We see still heartbreakingly elevated levels of new unemployment claims, with more than 19 million Americans recently receiving some form of jobless assistance," said Mark Hamrick, senior economic analyst at Bankrate. “This week’s dramatic events in Washington may have forced an elevation of the middle ground and a reckoning of understanding that constructive solutions are needed to address the pandemic and economy-boosting measures including infrastructure funding."
Thursday's numbers come one day after a report from payroll processing company ADP, which showed the total number of people employed fell in December for the first time since April. Payrolls fell by 123,000 last month, compared to forecasts of an increase of 60,000.
Focus now turns to Friday's closely watched jobs report, the last employment snapshot under Trump, which is expected to show the lowest monthly total since April. Economists forecast that just 50,000 jobs were added for the month of December and the unemployment rate rose to 6.8 percent.
U.S. sets new daily records for Covid deaths, cases; California reports 530 dead in a day
The U.S. reported 3,920 Covid-19 deaths and 268,840 new cases Wednesday, two new records amid a worsening pandemic.
Since the start of the pandemic as of Thursday morning, 361,999 have died of Covid-19 and 21.4 million have been infected, according to NBC News' count.
California reported 530 dead, a single-day record in the state.
These states also set single-day records in cases Wednesday:
- Louisiana, 6,876 cases
- Nevada, 60 dead
- New Hampshire, 24 dead
- New York, 16,707 cases
- Oklahoma, 62 dead
- Virginia, 5,387 cases