What you need to know about coronavirus on Friday, July 3

But warnings by medical experts that this weekend's gatherings could produce a disastrous spike in infections continue to be ignored by some of the country's top officials. President Donald Trump will travel today to South Dakota for an early Fourth of July celebration at Mt. Rushmore. Those attending the fireworks display and flyover won't be required to wear masks or practice social distancing, unlike the guests at the White House party tomorrow.

Dr. Jonathan Reiner, who was an adviser to the White House medical team under President George W. Bush, said Trump is "clearly flirting with disaster" by holding rallies and attending events without wearing a mask. "[He]is over 70 and he's obese. He probably has close to a 20% chance of dying if he contracts the virus," Reiner told CNN.

Trump has made significant efforts to downplay -- or outright ignore -- the pandemic in recent weeks, painting a rosy picture of the administration's response and pushing reopenings despite the fact that 36 states are currently experiencing a rise in new cases.

Florida, Texas and Arizona -- states that aggressively embraced Trump's demands to get the economy open -- are heading into what one expert described as a viral threat approaching "apocalyptic" levels.

Some are rethinking their strategies. In a stunning turnaround, Texas Governor Greg Abbott yesterday ordered most Texans to wear face coverings in public. This is the same man who, just two months ago, issued an executive order expressly banning local jurisdictions from fining those who refuse to wear a mask in public.

Still, there are some who are refusing to budge. Florida has paused the reopening, but Governor Ron DeSantis has said the state will not revert to stricter measures to curb the worsening outbreak.

YOU ASKED. WE ANSWERED

Q: If the antibodies may or may not offer long-term immunity, how would a vaccine help?

A: In some cases, a vaccine might give stronger protection than antibodies produced after being infected, epidemiologist Dr. Larry Brilliant said. "There are actually six other coronaviruses -- MERS and SARS and four other viruses that create the common cold. They don't seem to do very well at creating long-term immunity," Brilliant said.

"But we need to find out whether we can create a vaccine that creates more immunity [to the novel coronavirus] than the disease does. And that's not so wild. Many of the vaccines that we've made in history are actually stronger than the virus is itself at creating immunity."

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WHAT'S IMPORTANT TODAY

Here's what happened when the US and Brazil lifted lockdowns

Patience in lifting coronavirus restrictions is paying off, but easing lockdowns too early can have deadly consequences.

A CNN analysis of policies across 18 nations has shown that most of the countries that have now been designated by the European Union as having the epidemic under control only started easing their regulations after seeing sustained drops in daily new cases of Covid-19.

In contrast, three of the four countries with the world's highest death tolls and case counts -- the US, Brazil and India -- have either never properly shut down or started reopening before their case counts began to drop.

New mutation of the virus is spreading faster

A global study has found strong evidence that a new form of the coronavirus has spread from Europe to the US, Maggie Fox writes. The new mutation makes the virus more likely to infect people but does not seem to make them any sicker than earlier variations of the virus, an international team of researchers reported yesterday.

The study, published in the journal Cell, says the mutation affects the spike protein -- the structure the virus uses to get into the cells it infects. Researchers are now checking to see whether this affects whether the virus can be controlled by a vaccine.

'Sending the population to the slaughterhouse'

Like many places in Brazil, Rio de Janeiro is relaxing restrictions -- despite warnings from experts that the city has so far failed to bring Covid-19 under control.

Restaurants, bars and gyms in Rio were allowed to reopen yesterday, much to the dismay of health experts. "Governors and mayors are sending the population to the slaughterhouse with the prerogative of an economic recovery," said Domingos Alves, a computer modeling expert from the Covid-19 Brasil group, which brings together scientists from several Brazilian universities.

Brazil is the second worst hit country after the US. It has recorded nearly 1.5 million cases. More than 61,800 people have died.

Remember hydroxychloroquine? A new study suggests it may actually help

A new study found that the controversial antimalarial drug hydroxychloroquine helped patients better survive in hospital. This is a surprising finding. Several other studies have found the drug, originally developed to treat and prevent malaria, not only didn't help, but was also making patients more likely to suffer cardiac side effects.

But a team at Henry Ford Health System in Michigan said yesterday its study of 2,541 hospitalized patients found that those given hydroxychloroquine were much less likely to die. The difference? "What we think was important in ours ... is that patients were treated early. For hydroxychloroquine to have a benefit, it needs to begin before the patients begin to suffer some of the severe immune reactions that patients can have with Covid," said Dr. Marcus Zervos, the division head of infectious disease for Henry Ford Health System.

Singapore got coronavirus under control. Then dengue struck

The city-state is facing a new public health crisis with more than 14,000 dengue cases reported since the start of the year. The total number for the whole year is expected to exceed the 22,170 cases reported in 2013 -- the largest dengue outbreak in Singapore's history.

Climate change and rapid urbanization have made dengue outbreaks bigger in the past decades. But experts say the coronavirus lockdown measures might have worsened the outbreak this year. "When more people stay at home all the days, there could be more residential mosquito breeding and more opportunities for 'blood meals'," said Luo Dahai, associate professor of Infection and Immunity at Nanyang Technological University.

ON OUR RADAR

He posted his regrets over attending a party in California. The next day, he died of coronavirus.An outbreak in the Australian city of Melbourne has been linked to a quarantine hotel sex scandal.Face shields AND face masks are now mandatory on Qatar Airways. Walmart is transforming 160 of its parking lots into drive-in theaters. Kim Jong Un claimed North Korea's Covid-19 response has been a "shining success."At least 152 coronavirus cases have been linked to one Michigan bar. New York City's mayor said schools would reopen in the fall. The governor said not so fast.McDonald's has hit pause on reopening dining rooms as coronavirus cases rise.A groom in India died of coronavirus two days after his wedding. 80 people linked to the ceremony were infected.

TOP TIPS

A combination of factors could make the Fourth of July a "perfect storm" of coronavirus infections -- but only for those who don't choose to safely navigate the holiday weekend. So here's a guide on how to celebrate the Fourth of July from the safety of your home. There will be virtual tours of historical landmarks, the annual Nathan's Famous Hot Dog Eating Contest, S'mores, DIY confetti and backyard water parks. And of course, Hamilton.

TODAY'S PODCAST

"Sometimes I wonder how different things would've been if the virus was bigger and actually visible to the naked eye ... if we could see it flying out of the mouths and noses of those infected. Tethered by strings around six feet long. If we saw that, would we behave differently?" -- Dr. Sanjay Gupta

This Fourth of July isn't just a day of celebration -- it's a test of our discipline to slow the spread of the coronavirus. CNN Chief Medical Correspondent Dr. Sanjay Gupta talks to the United States as if it were his patient about how we can get back on track. Listen Now.