A Chinese university says scientists identified the heavily trafficked pangolin as a possible intermediary host of the new coronavirus while the number of new virus cases declined for a second day.

The coronavirus from China is believed to have originated in bats and transferred to humans through some other animal, health officials say. The pangolin may be that key link, researchers at South China Agricultural University said Friday.

“This latest discovery will be of great significance for the prevention and control of the origin of the new coronavirus,” South China Agricultural University said in a translated statement.

The research team tested more than 1,000 samples from wild animals and a found a 99% match between the genome sequences of viruses found in pangolins and those in human patients, the AFP reported, citing Chinese state media.

James Wood, a veterinary medicine professor at the University of Cambridge, told the French news agency that more data is needed and showing similarity between the genome sequences alone is “not sufficient.”

“You can only draw more definitive conclusions if you compare prevalence (of the coronavirus) between different species based on representative samples, which these almost certainly are not,” Dirk Pfeiffer, professor of veterinary medicine at Hong Kong’s City University, told Reuters.

Pangolins, the world’s only scaly mammal, have long been valued for their meat, viewed as a delicacy in some Asian countries, and scales, used for traditional medicine, according to the World Wildlife Fund.

Recent conservation efforts have worked to protect the eight pangolin species found in Asia and Africa and threatened by illegal international trade. More than 100,000 pangolins are poached every year, according to WildAid, a nonprofit that works on illegal animal trade.

News of their possible link to the coronavirus outbreak comes as the World Health Organization cautioned Friday against too much optimism after a decline in new cases over recent days.

“The numbers could go up again … but the last two days were showing a declining trend,” said WHO’s director-general Tedros Adhanom Ghebreyesus.

China reported 31,161 cases in mainland China in its update Friday. The rise of 3,143 was the lowest daily increase since at least Tuesday.

According to data collected by Johns Hopkins University as of Friday, 31,523 people have been infected and 638 killed from the outbreak that first appeared late last year.

The outbreak may have emerged from a market selling seafood and meat in Wuhan. Researchers theorize that someone bought contaminated meat at the market, ate it, got sick and infected others, creating a ripple effect around the world.

However, research in the British medical journal The Lancet suggests the outbreak started earlier than December and casts doubt on the market connection.

While the majority of cases and deaths have been in China, the virus has spread across continents, prompting the WHO to declare a “public health emergency of international concern.”

In the United States, 12 people have been infected, per Johns Hopkins. Federal health officials confirmed last week the first U.S. case of person-to-person spread of the virus.

President Donald Trump tweeted Friday he “had a long and very good conversation by phone with President Xi of China” on the country’s response to the coronavirus.

“He will be successful, especially as the weather starts to warm & the virus hopefully becomes weaker, and then gone,” Trump tweeted.

Contributing: Adrianna Rodriguez; The Associated Press