The US government's top infectious diseases expert has warned that daily Covid-19 cases could more than double if Americans fail to take counter- measures.
Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases, also cautioned against pinning hopes on a vaccine.
California, Texas and several other states are reporting record increases in cases of the sometimes deadly illness caused by the coronavirus.
Unless Americans wear masks and recommit to social distancing, the daily increase in new cases nationwide, currently around 40,000, could reach 100,000, Fauci told a US Senate committee.
"Clearly we are not in total control right now," Fauci said on Tuesday. I am very concerned because it could get very bad."
Covid-19 cases more than doubled in June in at least 10 states, including Texas and Florida, a Reuters tally showed.
More than 126,000 Americans have died from Covid-19.
Coronavirus cases more than doubled in 14 US states in the month of June, including California, Florida and Texas, a Reuters analysis on Tuesday showed.
In other international coronavirus developments:
Italian study finds 40% of coronavirus cases had no symptoms
A study of coronavirus infections that covered almost everyone in the quarantined north Italian town of Vò found that 40% of cases showed no symptoms - suggesting that asymptomatic cases are important in the spread of the pandemic.
The study, led by a scientist at Italy's Padua University and Imperial College London, also produced evidence that mass testing combined with case isolation and community lockdowns can stop local outbreaks swiftly.
"Despite 'silent' and widespread transmission, the disease can be controlled," said Andrea Crisanti, a professor at Padua and Imperial who co-led the work.
"Testing of all citizens, whether or not they have symptoms, provides a way to ... prevent outbreaks getting out of hand."
Brazil deaths approach 60,000
Nearly 60,000 people have died from Covid-19 in Brazil, confirming the South American nation has the second-highest number of coronavirus cases and fatalities in the world.
According to Health Ministry data on Tuesday 59,594 people have now died from coronavirus with the total number of confirmed cases rising by 33,846 to reach 1,402,041.
The Brazilian government led by the populist far-right President Jair Bolsonaro has been criticised for belittling the risk posed by coronavirus which he dismissed as "a little cold" at the start of the pandemic.
Airbus to cut 15,000 jobs to survive coronavirus crisis
Airbus is cutting 15,000 jobs within a year, including 900 already earmarked in Germany, saying its future is at stake after the coronavirus outbreak paralysed air travel.
The company is moving swiftly to counter damage caused by a 40 percent slump in its 55-billion-euro jet business following the pandemic, balancing belt-tightening against aid offered by European governments and future priorities.
But it faces tough talks with governments as well as unions, which immediately pledged to fight compulsory redundancies.
USFDA releases guidance for Covid-19 vaccine approval
The US Food and Drug Administration on Tuesday released guidance for approving a coronavirus vaccine, saying the vaccine has to prevent or decrease disease severity in at least 50 percent of people who are inoculated.
More than 100 vaccines are being tested worldwide against the virus.
South Korea begins supply of Gilead's remdesivir -KCDC
South Korea started supplying Gilead's antiviral drug for the treatment of the novel coronavirus on Wednesday, the Korea Centers for Disease Control and Prevention said.
The first batch of remdesivir will come from Gilead's donation until July, while the health authorities will negotiate the price for supply after August, the organisation said in a statement.