The coronavirus that causes Covid-19 may have spread beyond China before the health authorities had even discovered the disease, according to the Italian professor who recently said there had been “very strange pneumonias” in Europe as early as November last year.

The comments by Giuseppe Remuzzi, director of the Mario Negri Institute for Pharmacological Research in Milan, during an interview with US National Public Radio last week were quickly seized upon in the increasingly acrimonious blame game between Washington and Beijing.

Remuzzi’s comments attracted much attention in China, where the authorities have been working hard to steer the international narrative about the pandemic, and stop people describing it as the “China virus” or “Wuhan virus” after the city where the disease was first identified.

In an interview with the Chinese science and technology news outlet DeepTech, which was published on Tuesday, Remuzzi said the key point in his NPR interview was not where the virus came from, but how far it had spread before it was discovered.

He said a major question was how long the disease, which has so far infected more than 378,000 and killed over 16,500 people worldwide, had been spreading in China before health authorities realised its severity.

Taking into account the long incubation period, Remuzzi said he would not be surprised if some asymptomatic carriers had travelled around China or even abroad before December.

The professor also said that while it was possible it originated outside Wuhan, there had so far been no proof to support the theory.

As the outbreak gathered pace in the US, where it has now killed more than 500 people, Washington has escalated its rhetoric. President Donald Trump had repeatedly referred to it publicly as the “Chinese virus” until he changed tone on Monday and declined to use the phrase.

China, meanwhile, has described the rhetoric adopted by “certain US politicians and senior officials” as an attempt to defame and stigmatise China over the pandemic.

A number of Chinese state media outlets, including party mouthpiece People’s Daily and its tabloid affiliate Global Times, seized on Remuzzi’s comments about “strange pneumonias” to counter the “Chinese virus rhetoric”.

In the NPR interview, Remuzzi tried to explain why Italy had been caught off guard when the outbreak started gathering pace in February.

He discussed the difficulty of combating a disease that people did not know existed, and said the unusual cases in November and December could mean that virus was already circulating in Lombardy, the country’s worst-hit region, before people were aware of what was unfolding in Wuhan.

Remuzzi also shared details of the early suspected cases in Lombardy with DeepTech and Chinese state-run international network CGTN.

Remuzzi said he had learned about the cases from a few general practitioners and he has not yet been able to verify the information.

But he said there are some other suspicious cases he “knows for sure”, including two pneumonia cases in Scanzorosciate in northern Italy in December, where the patients developed high fever, a cough and had difficulty in breathing.

He said there had also been 10 patients who developed bilateral interstitial pneumonia in two other nearby towns, Fara Gera D’Adda and Crema, who had similar symptoms.

Remuzzi said local doctors considered these cases to be “unusual” but ruled out the possibility of seasonal influenza, as all these patients had been vaccinated.

“The reason we don’t know if it was Covid-19 is because at that time this could not be tested; the patients didn’t have X-rays,” he told CGTN.

They recovered within 15 days, with some receiving two or three courses of antibiotics.

Remuzzi added there had also been a patient diagnosed with bilateral interstitial pneumonia in Alzano Lombardo Hospial in Lombardy around the time.