Uber’s one-time, $9.4 billion stake in Chinese ride-hailing giant Didi has dwindled by half in less than a month as China escalates its threats to U.S.-listed companies. More than $2 billion of the drop came this week.

Didi’s American depositary shares, which debuted at $14 a piece in June on the New York Stock Exchange, plunged 21% on Friday to $8.02, after falling 11% a day earlier. They had reached a closing high of $16.40 on July 1, the second day of trading.

Uber owns about 12% of Didi, making it the second-largest investor behind SoftBank. Uber obtained its stake in 2016 after selling its Chinese business to Didi in exchange for equity in its rival.

Didi’s IPO came with a lot of hype and a market cap of close to $70 billion. But the honeymoon was short-lived, as within days of the offering separate reports surfaced that Chinese officials were conducting a cybersecurity review of the company and that Didi had been advised to postpone its listing and review its network security weeks before it went public.

The news worsened this week, after Bloomberg reported that Chinese regulators are planning punishments against Didi, including a fine that could exceed the record $2.8 billion Alibaba paid earlier this year after an anti-monopoly investigation. Didi did not respond to requests for comment on the Bloomberg report earlier this week.

Penalties could include delisting or withdrawal of U.S. shares, Bloomberg reported, citing people familiar with the matter. Chinese lawmakers have announced plans of late to limit the ability of domestic companies to list overseas.

While Uber is still showing a profit from its initial investment in Didi, valued at about $2 billion five years ago, it’s falling fast. At the end of March, Uber valued the stake at $5.9 billion in its quarterly filing. As of Friday, it’s down to $4.6 billion.

Uber isn’t the only company getting hit by Didi’s drop. SoftBank’s stake has fallen from close to $14 billion after the IPO to under $8 billion. Tencent, the Chinese internet conglomerate, has seen the value of its Didi holdings fall to $2.5 billion from about $4.3 billion.

Uber’s shares have held up this week, rising 2.3% to $47.26.

Covid cases are on the rise in all 50 states and the District of Columbia as the delta variant rapidly spreads across the U.S. and the virus once again tightens its grip.

The U.S. is reporting an average of about 43,700 new cases per day over the past week — far below pandemic highs but up 65% over the previous seven days and nearly three times as high as the level two weeks ago, data compiled by Johns Hopkins University shows. Cases hit a 15-month low in late June before they began to rise yet again as fewer people got vaccinated and the more infectious delta variant took hold in the country.

Vaccination rates peaked in April at more than 3 million shots per day but have dropped off considerably in recent months to around 530,000 a day, according to data compiled by the Centers for Disease Control and Prevention.

Louisiana, Arkansas, Missouri, Florida and Nevada are reporting the highest daily average of new cases per capita over the past week, all of which are at least double the U.S. rate.

Each of those states also have vaccination rates below the nationwide level, with the biggest gap visible in Louisiana, where 47.7% of the eligible age 12-plus population has received one shot or more compared with 65.9% for the country overall.

Hospital admissions of Covid patients are up 32% compared with one week ago, according to the Centers for Disease Control and Prevention. The count of daily Covid deaths, which typically lag an increase in case counts by a few weeks or more, has ticked upward but not at the same pace as cases or hospitalizations. Many Americans most vulnerable to the virus also now have some level of protection, as 89% of seniors have received at least one shot.

“Deaths haven’t risen because we have done an incredible job of fully vaccinating the populations most likely to die from Covid-19, especially those over 65 and nursing and assisted home residents,” Dr. Peter Chin-Hong, infectious disease specialist at the University of California at San Francisco, said in an interview. “Deaths also lag infection rate in a few cases, but I also anticipate the death rate not to budge.”

The overwhelming majority of serious Covid cases — 97% of hospital admissions, and 99.5% of Covid deaths — are occurring among those who are not vaccinated, U.S. Surgeon General Vivek Murthy told reporters at a White House briefing Thursday.

President Joe Biden and CDC Director Dr. Rochelle Walensky have both called the current state of the outbreak “a pandemic of the unvaccinated.”

U.S. officials are pleading for Americans to get vaccinated against the delta variant, which Walensky said is one of the most infectious respiratory diseases ever seen by scientists. At 68.6% of the adult population at least partially vaccinated, the U.S. has still not reached Biden’s July Fourth goal of getting 70% of Americans aged 18 and older to receive one shot or more.

The variant is highly contagious, largely because people infected with the delta strain can carry up to 1,000 times more virus in their nasal passages than those infected with the original strain, according to new data.

“The delta variant is more aggressive and much more transmissible than previously circulating strains,” Walensky told reporters at a briefing Thursday. “It is one of the most infectious respiratory viruses we know of, and that I have seen in my 20-year career.”

Local officials across the country are now pleading with Americans to once again wear masks indoors. Several counties in California and Nevada are now advising all residents to wear masks in public indoor settings — whether they are vaccinated or not. Local leaders in at least three more states have reinstated mask mandates, issued facial covering recommendations or threatened the return of strict public health limits for all residents — in defiance of CDC guidelines that say vaccinated people don’t have to follow those protocols in most settings.

“The easiest and best and most effective way that we can prevent the emergence of a new variant and crush the already existing delta variant is to get everyone vaccinated,” said White House chief medical advisor Dr. Anthony Fauci in an interview Wednesday with CNBC.

— CNBC’s Bob Towey contributed reporting.