A study has found that the new coronavirus appears to weaken more quickly under sunlight, higher temperatures and humidity, the U.S. government said Thursday, while warning against optimism that the summer season will bring an end to the pandemic.

"Our most striking observation to date is the powerful effect that solar light appears to have on killing the virus, both surfaces and in the air," William Bryan of the Department of Homeland Security said at a press conference also attended by President Donald Trump.

(Electron micrograph shows the new pneumonia-causing coronavirus.)[Courtesy of the U.S. National Institute of Allergy and Infectious Diseases]

But Bryan admitted it would be "irresponsible for us to say that we feel that the summer is just going to totally kill the virus" and called for people to continue to heed the social distancing guidelines to slow its spread.

According to the study conducted at a biocontainment laboratory in Maryland on nonporous surfaces, such as door handles and stainless steel, it took 18 hours for coronavirus particles to decrease by half in a dark, low-humidity environment where the temperature was between around 21 C and 24 C.

But the so-called half-life of the virus dropped to six hours in a high-humidity environment and to two minutes when also exposed to sunlight. Under increased temperature and high humidity without sunlight, the half-life was one hour.

When the coronavirus was suspended in the air, its half-life was 90 seconds with sunlight and low humidity, compared with one hour in the absence of sunlight.

Bryan said the figures are "emerging results" and that the research will continue. The Trump administration appears to have been eager to introduce the findings as it pushes to reopen the economy that has been shut down due to the pandemic.

The United States has the world's highest number of confirmed coronavirus cases, exceeding 860,000, according to a tally by Johns Hopkins University. The death toll has reached nearly 50,000.

Meanwhile, in the hardest-hit state of New York, a study to look into the infection rate is being conducted from Sunday, with a preliminary result showing that 13.9 percent of those tested had antibodies against the new coronavirus.

The figure equates to an estimated 2.7 million infections statewide -- 10 times higher than the officially announced figures. The survey tested 3,000 people at grocery stores and other box stores over two days across the state, according to New York Gov. Andrew Cuomo.