The new coronavirus can easily infect the cells of the airways of the human lung and in fact is as adept at doing so as a common cold virus, a new study reports.
The authors say the findings suggest this new virus is already well-adapted to being a human pathogen.
There are six confirmed deaths from a new coronavirus infection. (Beth Fischer/Canadian Press) The new research finding was published in the journal mBio on Tuesday, the same day British health officials announced that the new coronavirus had taken another life. The unidentified man's death brings to six the number of people confirmed to have died from the new infection.
The man, who had another illness that may have made him more susceptible to infection, is believed to have been infected by a relative, a British resident who became ill while travelling recently in Pakistan and Saudi Arabia. The father remains in serious condition in hospital.
A third member of the same family has also been confirmed to have been infected, but is reported to be suffering from minor symptoms only.
The cluster of cases is not the first in which person-to-person spread is suspected, but in two previous clusters questions remain about whether the virus spread from person to person, or from a source in nature to each.
In the British cluster, the likelihood of person-to-person spread is strong, Britain's Health Protection Agency acknowledged. Neither the second nor the third case in the cluster had recently travelled outside the United Kingdom.
"The three recent cases in the U.K. represent an important opportunity to obtain more information about the characteristics of this infection in humans and risk factors for its acquisition, particularly in the light of the first ever recorded instance of apparently lower severity of illness in one of the cases," John Watson, head of the respiratory diseases department at the agency, said in a statement announcing the death.
Lung experiments
In the new study, Volker Thiel and colleagues tested the new virus in human bronchial cells in a system that mimics the environment of the lining of the airways of the upper lung.
They compared the new EMC virus, as it is called, with the virus that caused SARS and one called 229E that causes colds in people.
All three are members of the coronavirus family.
The cells were as susceptible to the EMC virus as to the other two and in fact, the new virus multiplied at a faster rate than the SARS virus did in the human cells.
Thiel is with the Institute of Immunobiology is at the Kantonal Hospital in St. Gallen, Switzerland. He also teaches at the University of Zurich. Other scientists on this project are with the University of Bonn Medical Centre, the Helmholtz Center for Infection Research in Braunschweig, Germany and Erasmus Medical Centre in Rotterdam, the Netherlands.
Thiel said the team was not surprised that the new virus could infect the airway cells — called epithelial cells — because it has already infected people. But the degree of susceptibility of the cells to the new virus was unexpected.
"We were a bit surprised that it can so easily infect those cells," he said in a telephone interview.
"Usually you think that there is a so-called species barrier when an animal virus gets into a human population. But at least on the epithelium layer, we don't see that."
The new virus was first spotted last June, when a Saudi Arabian man died from an initially unidentified respiratory infection. Since then, cases have emerged sporadically — some singly, others in small groups. As well, testing on stored samples revealed two people who died in a mysterious respiratory outbreak in Jordan last April were infected with the EMC virus.
Unanswerable questions
All of the infections appear to have a link to the Middle East, with Saudi Arabia, Jordan and Qatar being the three countries from which most cases have arisen.
Of the 12 confirmed cases, six have died and several more remain gravely ill in hospital. In addition to the confirmed cases, the World Health Organization considers a number of other people as probable cases, including nine more people who were ill in the April 2012 outbreak in Jordan.
The source of the new virus is still unknown. As such, there are many unanswered — and currently unanswerable — questions about how much of a risk the virus poses to people. No one can say at this point whether it will fade away, continue to trigger the occasional infection or start to spread easily from person to person.
But the question of whether the virus would need to evolve more to gain the power to infect human lungs does seem to have been answered.
"If an animal virus gets into the human population, one assumes that some adaptation is needed," Thiel said.
"As we have seen for instance for SARS, there was a phase of adaptation to the human cells, to the receptor. And obviously that is not needed for this new coronavirus."
Still, he cautioned that just because the virus can easily infect human lung cells doesn't mean it has all the tools it would need to take off and spread widely among people.
"We have shown that the airway cells can easily be infected. But this does not mean that the virus can easily be transmitted," Thiel said. "I think this distinction is important."
The study also found that all three coronaviruses seem to be able to slip past the immune system because they don't trigger much of an innate immune response. The innate immune system is the so-called first line of defence.
The researchers found, though, that if they treated the cells with interferons — signalling proteins that cells release to warn surrounding cells of the presence of an attacker — the number of infected cells was significantly reduced.
That finding opens up the possibility that interferons, which are currently used in the treatment of some viral diseases, could be used to treat infection with the EMC virus, Thiel said.
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