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(CNN)Faster tests combined with a "robust" immune response against Covid-19 could soon mean a slower spread, researchers said.
Tests have been delayed and in short supply as the United States surpassed 5.4 million cases, leaving many uncertain about their risk of spreading the virus. And as researchers rush to develop vaccines, they've had little evidence to tell if antibodies that protect against Covid-19 last long enough to get the virus under control. But developments from researchers Monday brought optimistic outlooks to both fronts.
SalivaDirect, a test that does not require specialized supplies and can deliver results in less than three hours, could be available to the public in a matter of weeks, according to Anne Wyllie, an epidemiologist at Yale School of Public Health who was part of the team responsible for the protocol.
"It skips so many steps up front, so it makes it much more amenable to be used as a surveillance tool like in schools or universities," Dr. Brett Giroir, the White House coronavirus testing coordinator, told ABC's "Good Morning America" on Tuesday.
And though many are in early stages and have not been peer-reviewed, a recent batch of studies show that humans -- even those with mild symptoms -- have a "robust" immune response to coronavirus that could provide evidence that a vaccine could protect the public for more than just a short period of time, said Dr. Ian Lipkin, director of the Center for Infection and Immunity at Columbia University Mailman School of Public Health.
"This is very good news and it's optimistic," Lipkin said Monday. "You know, it is a bit of blue sky that we've been looking for."
How long that protection lasts is still unclear, but the studies indicate it could last for months.
The news comes as the White House coronavirus task force coordinator said Monday she wished the early days of coronavirus in the US looked more like it did in Italy: strict lockdowns keeping people home as infections spread.
Positivity rates are dropping, but deaths have been above 1,000 daily since late July
The average number of daily, official new coronavirus cases reported in the US has been declining for weeks. But daily deaths -- which experts say can spike weeks after a jump in new cases -- have recently been at a relatively elevated level.
Daily new cases over the past week averaged about 49,100 as of Monday, down from more than 65,000 per day in mid-to-late July, according to Johns Hopkins University data. Daily testing also has declined, however, since late July, according to the Covid Tracking Project.
The seven-day average of test-positivity rates in the US dropped to 6.6% as of Tuesday, down from 8.5% in mid-July, according to the Covid Tracking Project.
The CDC's director has suggested communities' positivity rates should be below 5% to comfortably reopen schools. At least 24 states averaged above 5% as of Monday.
Still, the country's seven-day average for daily Covid-19 deaths has been above 1,000 for 22 straight days as of Monday, after seven weeks of below 1,000.
Los Angeles County, a hotspot in California, has seen steady progress in the fight to curb the virus, LA County Public Health Director Barbara Ferrer said Monday. Daily hospitalizations have dropped 37% in the last month.
"We do continue to be cautiously optimistic that all the sacrifices and the hard work that we've seen across our county is working and that we're in fact back to slowing the spread," Ferrer said.
Texas on Monday became the fourth state to surpass 10,000 Covid-19-related deaths. And Florida nearly doubled its count of coronavirus deaths in just a month, bringing the total to 9,539.
Georgia, Florida and Texas led the nation for highest per-capita rate of average new daily cases as of Tuesday morning, according to CNN's analysis of JHU data.
However, Florida Gov. Ron DeSantis tweeted Monday that the state is reporting the lowest number of cases of Covid-19 in one day since mid-June at 2,760; adding that the number of coronavirus-positive patients hospitalized in the state is down almost 40% since July 21.
Schools at decision point as researchers learn more about coronavirus in youths
Health experts learning more about how young people are contracting and spreading the virus must decide if and how to bring students back to school for the new academic year.
A common perception is that young people don't need to worry about being infected, the director of the National Institute for Allergy and Infectious Diseases Dr. Anthony Fauci said Monday. But researchers have found that even those not hospitalized can have "really troublesome" long-term effects.
"In individuals who are young and otherwise healthy, who don't require hospitalization but do get sick and symptomatic enough to be in bed for a week or two or three and then get better, they clear the virus -- they have residual symptoms for weeks and sometimes months," he said during a American Society for Microbiology briefing.
"These are people that supposedly recovered from Covid-19," he said.
Meanwhile, many schools that have resumed instruction in-person have quickly reported infections.
In Florida, more than 25 districts are due to have started in-person instruction by week's end. Three districts -- those of Baker, Bradford and Martin counties -- reported having to place students in quarantine after a week of in-person classes. Martin County alone has quarantined 292 students, district spokeswoman Jennifer DeShazo said Tuesday.
The University of North Carolina at Chapel Hill abruptly decided this week it will no longer hold in-person undergraduate classes on campus, starting Wednesday, after about 130 students tested positive for Covid-19 in the first week since classes began.
The Los Angeles Unified School District, meanwhile, says it will provide regular Covid-19 testing and contact tracing to all students and staff, and to families of those who test positive.
The school district -- the country's second-largest with more than 600,000 students -- is beginning the new school year without in-person classes. The hope, Superintendent Austin Beutner told CNN Tuesday, is to build a foundation for when the district opens for in-person learning.
"If we want to keep schools from becoming a petri dish and we want to keep all in the school community safe, we need to test and trace at schools," he said.
Study: No apparent racial difference in Covid-19 death rates if there's equal access to health care
If Black coronavirus patients are given the same access to hospital care as White patients, their death rates in the hospital appear not to be different, according to research published Tuesday in the journal JAMA Network Open.
The research found no difference in mortality among Black and White patients hospitalized for coronavirus infection, after adjusting for sociodemographic and clinical factors.
Dr. Baligh Yehia of Ascension Health in Missouri and colleagues studied 11,210 adult coronavirus patients between February and May in 92 hospitals across 12 states. They found no statistical difference in the risk of mortality between White and Black patients, after adjusting for age, sex, insurance status, comorbidity, neighborhood deprivation and site of care.
Of the 11,210 patients, 37.3% were Black. Black patients were younger, more likely to be women and more likely to have Medicaid insurance than their White counterparts. Black patients were also more likely to have other health conditions such as asthma, cancer, chronic kidney disease, congestive heart failure, diabetes, hypertension and obesity.
About 63.7% of patients were hospitalized and 39.4% were Black. After adjusting for outside factors, the team found that mortality was 19.2% among Black patients and 23.1% among White patients. The overall mortality rate was 20.3%.
Similar rates of Black and White patients needed an intensive care unit. Among those in the ICU, 35.2% of Black patients died and 36.4% of White patients died.
The researchers note that across the US, Black people have experienced higher Covid-19 case rates and death rates.
"Although current reports suggest that Black patients represent a disproportionate share of COVID-19 infections and death in the United States, in this study, mortality for those able to access hospital care did not differ between Black and White patients after adjusting for sociodemographic factors and comorbidities."
They called for additional research on coronavirus mortality by race.
CNN's Artemis Moshtaghian, Topher-Gauk Roger, Amanda Watts, Lauren Mascarenhas, Jason Hanna, Eric Levenson, Naomi Thomas and Jen Christensen contributed to this report.
