South Korea records highest new daily coronavirus case numbers since March

Mexico recorded 5,267 new cases of Covid-19 and 626 virus-related fatalities on Wednesday.

This raises the country's total to 573,888 cases and 62,076 deaths.

Mexico has reported the third-highest number of deaths from coronavirus, behind only the United States and Brazil, according to Johns Hopkins University.

Within Latin America, Mexico has seen the third-highest number of total cases, following Brazil and Peru.

South Korea recorded 441 new coronavirus cases in the past day, marking the highest number of new daily cases since March 7, according to data from South Korean Centers for Disease Control and Prevention (KCDC).

Among the new cases, 434 were locally transmitted. Of these, 313 were from the Seoul metropolitan area, health ministry officials said Thursday. 

Meanwhile, officials continue to conduct contact tracing in relation to the Sarang-jeil Church cluster; more than 900 cases have been linked to it so far.

On top of the initial 4,066 close contacts of the Sarang-jeil Church congregation and visitors, an additional 1,846 people have been identified through on-site contact tracing, officials said today.

Meanwhile, Gwangju City Mayor Lee Yong-sub issued an executive order on Thursday, banning all religious gatherings and shutting down facilities used by the public.

Peru’s Health Ministry recorded 5,996 new coronavirus cases on Wednesday, bringing the total number of infections identified in the country to 613,378.  

The Health Ministry also confirmed 123 new fatalities, taking the country's coronavirus death toll to 28,124.

Only Brazil has recorded more Covid-19 cases in Latin America than Peru, according to Johns Hopkins University.

The US Centers for Disease Control and Prevention (CDC) made controversial changes to its testing guidelines after “updated recommendations” from the White House coronavirus task force, CDC Director Dr. Robert Redfield said Wednesday. 

The changed guidelines: The Trump administration has scrambled to explain the quiet changes made to the CDC website Monday.

The previous guidelines recommended testing anyone who had been in close contact with a confirmed case, even people who do not develop symptoms. The new guidelines said only some people should get tested.

Controversy over official approval: Earlier, Adm. Brett Giroir, who heads testing efforts for the task force, told reporters that task force members had weighed in on the change -- including Redfield and Dr. Anthony Fauci, the nation's top infectious disease expert.

But Fauci later denied this to CNN’s Dr. Sanjay Gupta.

The coronavirus pandemic is worsening the United States' drug shortage problem, according to the Food and Drug Administration (FDA).

Traditionally, Jensen said, drug shortages are rooted in manufacturing and quality problems involving sterile, injectable drugs especially older ones. Those are the very kinds of medications used by hospitalized patients, that are facing shortages and increased demand

There are also shortages of pharmacy drugs, like those for high blood pressure and antibiotics.

Jensen said the FDA had been in contact with more than 180 drug manufacturers since January, working to stabilize supply chains and monitor potential disruptions.

Medical personnel treat a coronavirus patient in the Intensive Care Unit of the Santa Casa de Misericordia Hospital on August 13 in Porto Alegre, Brazil. Silvio Avila/AFP/Getty Images

Brazil’s Health Ministry reported 47,161 new Covid-19 cases over the past 24 hours on Wednesday, bringing the country's total to 3,717,156.

The ministry also reported 1,086 new coronavirus fatalities, raising Brazil's death toll to 117,666.

Calculations by CNN based on official figures show that average cases and deaths in Brazil -- measured over a seven-day period -- peaked in late July.

For new cases, the peak average was 46,393 on July 29. As of August 26, that daily average had fallen to 37,214. 

There's been a slower decline in the average number of deaths -- from a peak of 1,096 on July 25 to 938 on August 26.

Only the United States has recorded more coronavirus cases and deaths than Brazil.

The US Centers for Disease Control and Prevention abruptly changed its Covid-19 testing guidelines. Now, the center no longer recommends testing for most people without symptoms -- even if they've been in close contact with someone known to have the virus.

Here's what we know so far about these new guidelines:

A syringe containing either the vaccine or a placebo is prepared for a participant in a Phase 3 Covid-19 vaccine clinical trial sponsored by Moderna at Accel Research Sites on August 4 in DeLand, Florida. Paul Hennessy/NurPhoto/Getty Images

Moderna's experimental coronavirus vaccine appears to be safe and elicits an immune response in all age groups, including the elderly, a company official said Wednesday.

Data from the phase 1 safety trial of the vaccine showed only mild adverse effects, and generated an immune response in volunteers aged 18 to 71, Dr. Jacqueline Miller, therapeutic area head for infectious diseases at Moderna, told a meeting of the Advisory Committee on Immunization Practices.

The phase 1 trial was conducted in three age groups: 18 to 55, 56 to 70 and 71 plus years of age. Participants received two 100mg doses of the vaccine 28 days apart. 

Neutralizing antibodies -- which inactivate the virus -- were detected in all participants, including the upper age range, she told the meeting. All age groups also seemed to produce the same immune response -- a good sign, as older people often have weaker responses to vaccines.

The most common adverse reactions were fatigue, chills, headache and myalgia. More reports of adverse symptoms were observed after the second dose of the vaccine, but the majority of symptoms resolved within two days. 

ACIP advises the US Centers for Disease Control and Prevention on how vaccines should be used in the population.