BEIJING, Jan. 14 (Xinhua) -- Researchers from the University of Milan have discovered that a woman in the northern Italian city was infected with COVID-19 in November 2019, according to media reports.

Through two different techniques on skin tissue, the researchers identified in a biopsy of a 25-year-old woman the presence of RNA gene sequences of the SARS-CoV-2 virus dating back to November 2019, according to Italian regional daily L'Unione Sarda.

"There are, in this pandemic, cases in which the only sign of COVID-19 infection is that of a skin pathology," Raffaele Gianotti, who coordinated the research, was quoted by the newspaper as saying.

"I wondered if we could find evidence of SARS-CoV-2 in the skin of patients with only skin diseases before the officially recognized epidemic phase began," said Gianotti, adding "we found 'the fingerprints' of COVID-19 in the skin tissue."

Based on global data, this is "the oldest evidence of the presence of the SARS-CoV-2 virus in a human being," the report said.

The findings in Italy are the latest among studies worldwide that have added to the growing evidence that COVID-19 was silently circulating outside of China earlier than previously thought.

In Brazil, the health department of the state of Espirito Santo announced on Tuesday that the presence of IgG antibodies, specific for SARS-CoV-2 virus, was detected in serum samples from December 2019.

The health department said that 7,370 serum samples had been collected between December 2019 and June 2020 from patients suspected of being infected with dengue and chikungunya.

With the samples analyzed, IgG antibodies were detected in 210 people, of which 16 cases suggested the presence of the novel coronavirus in the state before Brazil announced the first officially-confirmed case on Feb. 26, 2020. One of the cases was collected on Dec. 18, 2019.

The health department stated that it takes around 20 days for a patient to reach detectable levels of IgG after infection, so it could have occurred between late November and early December 2019.

In France, scientists found a man infected with COVID-19 in December last year, roughly a month before the first officially recorded cases in Europe.

Citing a doctor at Avicenne and Jean-Verdier hospitals near Paris, BBC News reported in May that the patient "must have been infected between 14 and 22 December, as coronavirus symptoms take between five and 14 days to appear."

In Spain, researchers at the University of Barcelona, one of the country's most prestigious universities, detected the presence of the virus genome in wastewater samples collected on March 12, 2019, the university said in a statement in June.

In Italy, research by the National Cancer Institute in Milan, published in November, showed that 11.6 percent of the 959 healthy volunteers who participated in a lung cancer screening trial between September 2019 to March 2020 had developed COVID-19 antibodies well before February when the first official case was recorded in the country, with four cases from the study dating to the first week in October last year, which means those people were infected in September.

On Nov. 30, a study by the U.S. Centers for Disease Control and Prevention (CDC) found that COVID-19 was likely in the United States as early as mid-December 2019, weeks before the virus was first identified in China.

According to the study published online in the journal Clinical Infectious Diseases, CDC researchers tested blood samples from 7,389 routine blood donations collected by the American Red Cross from Dec. 13, 2019 to Jan. 17, 2020 for antibodies specific to the novel coronavirus.

COVID-19 infections "may have been present in the U.S. in December 2019," about a month earlier than the country's first official case on Jan. 19, the CDC scientists wrote.

These findings are yet another illustration of how complicated it is to solve the scientific puzzle of virus source tracing.

Historically, the place where a virus was first reported has often not been that of its origin. The HIV virus, for instance, was first reported by the United States, yet it's believed that the virus originated outside of the U.S. Meanwhile, evidence has proved that the Spanish Flu did not originate in Spain.

Regarding these studies, the World Health Organization (WHO) said it will "take every detection in France, in Spain, in Italy very seriously, and we will examine each and every one of them."

"We will not stop from knowing the truth on the origin of the virus, but based on science, without politicizing it or trying to create tension in the process," WHO Director-General Tedros Adhanom Ghebreyesus said late November.