With the Middle East Respiratory Syndrome/novel Coronavirus (nCoV) and H9N7 influenza A virus exercising the best scientific minds in the World Health Organisation (WHO) and elsewhere at present, how worried should we be about these recently emergent viruses? Could we face another flu pandemic or a Sars scare?
These microbes present two quite distinct challenges: the H9N7 flu virus is a form of avian influenza, with its origins in fowl in China; the new coronavirus, on the other hand, is a completely novel virus first identified in patients in the Middle East last year.
To a large extent we have experience of what to expect from avian flu but nCoV represents an as yet unquantified threat to global health.
Good news
Probably the best news about the H7N9 virus is that since May 8th, no new laboratory-confirmed cases of human infection with this type of avian influenza have been reported to WHO. It suggests that authorities in China have been successful in their campaign of slaughtering all birds at chicken markets where the virus has been identified, thereby minimising the risk of human infection.
But Chinese and Taiwanese (a single case of human infection has been identified in Taiwan) health authorities and laboratories remain on high alert for additional cases and are especially vigilant in looking for any evidence of human-to-human transmission, which has not occurred to date.
Of 131 laboratory confirmed cases of human infection, some 36 people have died – an indication of the lethality of the bug in humans.
WHO assistant director general for health security, Keiji Fukuda, said last week "the immediate outbreak has been controlled, but it is also unlikely that the virus has simply disappeared. We believe we need go another autumn/winter/spring season to know." But he warned there was still a possibility the virus could develop the ability to spread easily from person to person, making a widespread influenza pandemic more likely.
“We also have high concern over the potential – I stress, the ‘potential’ – to gain the ability to sustain transmissibility,” Fukuda said.
And earlier this year the WHO official said that humans seem to catch H7N9 from birds relatively easily – more easily than they contract H5N1 bird flu, a strain that has killed people in the past.
Meanwhile, nCoV, which hit the headlines last September, remains somewhat of an enigma.
The first known case appeared in Saudi Arabia in early 2012; the second confirmed case was identified in a 49 year-old Qatari in September 2012, who had travelled to Saudi Arabia around the same time that the first case was identified.
But the virus has now spread beyond the Middle East, with cases now confirmed in the UK, France, Germany and, most recently, Tunisia.
Sibling cases
The two laboratory confirmed cases in the North African country are siblings – a 34-year-old man and a 35-year-old woman. Both had mild respiratory illness and did not require hospitalisation.
Future investigation into the cases revealed that their father became ill three days after returning from a visit to Qatar and Saudi Arabia on May 3rd. He was admitted to hospital after developing acute respiratory disease. His condition deteriorated and he died on May 10th.
Last week, one of 22 patients with nCoV in a concentrated outbreak at a healthcare facility in Eastern Saudi Arabia died. This brought the number of deaths worldwide to 21 out of a total of 43 confirmed cases of the virus.
All of the cases have had a direct or indirect connection to the Middle East, including two people who had travelled recently from the United Arab Emirates.
However, in France and the UK, there has been limited local transmission among close contacts who had not been to the Middle East but had been in contact with a traveller who recently returned from the region.
Among the many unknowns about nCoV is how exactly the virus spreads from person to person. All cases have occurred either in a healthcare facility or among close family members.
However, the mechanism by which transmission occurred in all of these cases, whether respiratory (by coughing, sneezing) or contact (contamination of the environment by the patient), remains a mystery.
The virus poses a particular threat to healthcare workers. Although the overall chance of contracting the virus is small, doctors around the world have been advised to be vigilant and to have a high index of suspicion in people with breathing difficulties that are not explained by any other illness and who have recently travelled to the Middle East.
For most Irish people, these viruses do not pose any immediate threat.
But as we have learned in the last decade, virology is a fast moving field; not many scientists are prepared to predict what may emerge in the future with “known unknowns” such as the H7N9 and nCoV microbes.
