A scientist who didn't work on the study told Newsweek it is "an impressive and important step forward."
Researchers looked at data on the Chinese city of Wuhan, the original epicentre of the COVID-19 pandemic, for their study.
The study involved almost 500 people in hard-hit Italy.
In the past few weeks, states in the south and west have experienced surges in cases
Scientists have conducted the biggest ever study on the condition.
Robert Redfield also said the outbreak could be brought under control if everyone wore masks.
A researcher looked at 39-years-worth of data from the annual Nathan's Famous Hot Dog Eating Contest held in New York City.
Scientists studied the diets of over 410,000 people.
Being sicker was linked to having more antibodies.
The two countries lead the world for COVID-19 cases and fatalities.
Persistent symptoms included fatigue and trouble breathing.
The research looked at more than 1,200 patients from 69 countries across six continents.
On Thursday, the U.S. hit another record high in reported daily cases at more than 64,000.
The small study involved 11 COVID-19 patients in Germany.
Kazakhstan officials have dismissed the reports as "fake news."
None of the patients who had the condition in the study tested positive for COVID-19.
The remarks could be viewed as a thinly veiled response to the Trump administration's decision to withdraw from the U.N. health agency.
Professor Cris S. Constantinescu told Newsweek: "We need to remain vigilant as even mild respiratory infection with COVID-19 can affect the nervous system in many different ways."
Experts told Newsweek a number of factors play into this seemingly contradictory trend.
Scientists looked at how different face coverings might protect people from a COVID-19 patient.
The state is among those to have been hit by a spike in COVID-19 cases in recent weeks.
The man was coughing up blood before he visited a hospital in Rhode Island.
Co-author Dr. Peter Kasson of the University of Virginia School of Medicine said: "The key finding is that individual actions matter."
Researchers reviewed seven existing studies on what is known as the gut-brain axis and pro and probiotics.
239 scientists from 32 countries signed a commentary entitled, "It is Time to Address Airborne Transmission of COVID-19."
In one month, approximately 300,000 more patients than usual were given hydroxychloroquine in the U.S., according to a study.
Three workers at the mine in China had died after developing pneumonia.
Scientists say variants of the coronavirus named D614 and G614 have differences in the spike protein the bug uses to invade our bodies.
Blood-clotting problems in patients with COVID-19 have been widely reported.