Amid confusion among health authorities and ordinary citizens about how seriously to take the new coronavirus, Beijing has pushed back against the decision by the US government to deny entry to foreigners who have recently travelled to China, and by US carriers to suspend their flights to and from the country.

Meanwhile, Americans returning from Hubei province – the epidemic’s epicentre – are being sent to quarantine centres for two weeks.

“The United States’ comprehensive ban on people coming and going between China … will bring some difficulties to implementing this agreement,” Wang told Reuters in Beijing. “I hope that the US will consider this problem, and continue to prevent the spread of this epidemic while not taking unnecessary limitations on trade and people.”

A LinkedIn post earlier this month by Mario Cavolo, an American public relations specialist based in China, resonated strongly among those questioning the US response.

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In the February 5 post, titled “Something’s Not Right Here Folks,” Cavolo draws a comparison frequently invoked by Beijing’s defenders: the reaction to the 2009 outbreak of an H1N1 influenza pandemic, an illness that the US Centres for Disease Control and Prevention (CDC) estimated to have led to as many as 575,400 deaths globally during the first year the virus circulated.

Estimates suggest that the H1N1 strain, which was first detected in the US, infected as much as 24 per cent of the world’s population.

Despite these staggering numbers, Cavolo pointed out, no countries turned Americans away or quarantined them. Nor did Washington come under sustained attack for initially undercounting the number of people infected.

However, charges that the US has overreacted to the spread of the coronavirus that causes Covid-19 have little purchase among public health experts.

Interviews with many of them turned up very similar responses, most pointing to an unsettling way in which human coronaviruses – of which only seven have ever been identified – mutate, compared with influenza strains, which have a lower fatality rate.

There are only four known types of human coronavirus that are not fatal; they each cause the relatively benign condition we know as the common cold. The only other human coronaviruses known to science – Sars, Mers, and the one that causes Covid-19 – have fatality rates above influenza pandemics, and there are no vaccines for any of them.

Conversely, humans eventually develop immunity to influenza strains like H1N1, so these contagions become less of a threat over time, and they are better understood by epidemiologists.

Despite the ground H1N1 covered globally, the CDC concluded that the epidemic killed only 0.001 to 0.007 per cent of the population.

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“Coronaviruses are not predictable,” said Kate Zaiger, an epidemiology master’s degree candidate at Harvard University’s T.H. Chan School of Public Health.

“With coronaviruses, it’s difficult for us to predict whether it’s going to die out, whether it’s going to mutate again, from the secondary mutation are we going to see a third mutation, is there going to be a tertiary mutation that’s going to make this completely unsolvable,” said Zaiger, who has a patent pending for a protein that she’s hoping will work in a future Covid-19 vaccine.

Zaiger cited the possibility that the new coronavirus had mutated since the initial outbreak in the Wuhan market into one that has aerosolised, meaning that it can now survive in the air and travel through ventilation systems to infect others.

She pointed to rising cases on a quarantined cruise ship docked off Japan’s coast as a possible example. While allowing that the 454 cases, including one death, now confirmed on the trip might have direct or indirect connections to Hubei province, the steady rise in these numbers might also be caused by droplets projected by the coughs of symptomatic passengers travelling to other cabins through the air.

“Zoonotic viruses usually continue to evolve on their animal hosts even when they disappear from human society,” said Jennifer Bouey, an epidemiologist and China policy specialist at the Rand Corporation.

Sars-CoV-2, the official name for the new coronavirus, has a 79 per cent genetic similarity to the 2003 Sars virus and is an 89 per cent match to a coronavirus Chinese scientists found in bats a few years ago, “so it is for sure that the virus ‘factory’ never stopped working in nature, and this new coronavirus happened to have jumped to humans and caused serious pneumonia”, Bouey said.

Gary Whittaker, a Cornell University professor of virology, agreed.

“The new coronavirus is much more of an unknown and so is getting much more attention – it has the potential to be a combination of both more widespread than Sars and more deadly than the 2009 H1N1 pandemic, and we are much further away from any medical countermeasures for coronaviruses,” Whittaker said.

“As a population we can accept and understand the flu and – with the exception of the 1918 influenza pandemic – basically deal with it, whereas the Sars and Mers coronaviruses have very high mortality rates and in general coronaviruses are much more unpredictable, hence the reaction,” he added.

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While most experts advocate an urgent response, not all of them agree that the travel bans and entry denials will halt the spread of Covid-19.

“Urgent response is warranted, but we do not have evidence to support these dramatic, urgent and wide-sweeping travel bans and cordons,” said Lauren Sauer, assistant professor of emergency medicine at the Johns Hopkins school of medicine.

“We are applying lessons we have learned in past outbreaks to respond to this new threat, with so many information gaps and so many unknowns. We are building the aeroplane as it is heading down the runway,” Sauer said.

Meanwhile, conspiracy theories and other concerns that lack scientific grounding have made it difficult to discount the role that xenophobia has played in the response.

Geopolitical concerns about China’s emergence as an economic power and freedom of speech issues had infected the overall global response to the contagion, said Robert Daly, director of the Wilson Centre’s Kissinger Institute on China and the United States.

“What we’re seeing is some tendency, with reference to the coronavirus, for the bad China narrative to eclipse the human sympathy narrative,” said Daly, who was a co-director of the Hopkins-Nanjing Centre for Chinese and American Studies at Nanjing University in China during the Sars outbreak.

“This is all true and this is going to make the situation worse.

“But because of concerns about China, geopolitically, I think that we are embracing the bad China narrative too quickly because it serves political ends and flatters ourselves, and doing that can mislead our analysis.”

This is the overarching point that Cavolo said he was driving at in his LinkedIn post.

“My article didn’t intend the comparison to be scientifically accurately perfect, that wasn’t the focus nor the message of the article, and meanwhile, I’m certainly not a virology expert,” he told the South China Morning Post. “My comparison was reasonable and sensible in terms of comparing the other aspects I was pointing out in the article.”

While anecdotes about people in the US avoiding Chinese restaurants and Chinatowns abound, one of the most high-profile “bad China” comments were made by Senator Tom Cotton, a Republican representing Arkansas, who last week suggested that the spread of the novel coronavirus might have been an unintended consequence of an alleged Chinese biological warfare programme.

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When Beijing’s ambassador to Washington, Cui Tiankai, was asked about the claim, and called the speculation “dangerous”, Cotton backed up his allegation by saying there was a virology lab in Wuhan’s outskirts, and the onus was on the Chinese government to disprove his assertion.

The Wuhan Institute of Virology, which houses China’s only level four biosafety laboratory, the highest-level classification for labs that study the deadliest viruses, is more than 30km (18.6 miles) from the epicentre of the current coronavirus outbreak.

Other US lawmakers, including Rick Scott, a senator representing Florida, have lined up to tie the Chinese government directly to the Covid-19 epidemic.

“Since Communist China cannot be trusted to coordinate in a transparent and efficient manner when it comes to combating the threat of the virus, every resource must be available to contain the disease and keep Americans healthy,” Scott said in an emailed statement on Thursday.

With so much built-up acrimony in the US-China relationship on so many fronts over recent years, few are optimistic that the response to Covid-19 will be based on objectively verifiable information.

“We have learned many lessons from the flu, lessons that have helped us with preparing for and responding to this current outbreak,” Johns Hopkins’ Sauer said. “However, we still have so much to learn.”