Carl Philpott, Professor of Rhinology and Olfactology at the University of East Anglia, explains how NHS health workers could have been unknowingly transmitting the virus in hospitals and to their families.
Loss of smell is a recognised symptom of COVID-19 in the UK. However, it was only added to the official list of symptoms on May 18, a full month after the World Health Organization recognised it as a symptom.
Before this time, any member of NHS staff reporting a loss of smell, especially in the absence of other symptoms, would not have been advised to self-isolate.
As the pandemic hit its peak in April, over 3,000 people were being admitted to UK hospitals a day. This meant many NHS staff were at risk, and given some of the problems that were faced with PPE, those who did develop symptoms needed to self-isolate.
Survey of NHS staff
In April and May 2020, at the height of the pandemic, we conducted a survey of hospital staff to find out how many of them had been affected by smell loss. And of those who had experienced smell loss, we wanted to know how many had it as an isolated symptom or before other symptoms appeared.
The survey was distributed to staff at hospitals in London, Norfolk and Greater Manchester. A total of 1,041 healthcare workers took part. Over half of the respondents were under the age of 40, and more than two-thirds were women.
The preliminary results of our study were published in The Lancet Microbe.
We found that nearly two-thirds of staff reported a sudden loss of their sense of smell or taste, or both, and that those affected were eight times more likely to have a positive test for COVID during the same period (April-May) than those without smell loss.
Four weeks after losing their sense of smell, only half the hospital staff surveyed had fully recovered it. A stark finding was that over half of those who lost their sense of smell continued to work, and many of those people were probably highly contagious at the time.
In nearly one in five cases, loss of smell was reported as the only symptom. And in one in three of those cases, it occurred before other symptoms appeared.
Smell distortions and burning or tingling in the nose and mouth were also experienced by one in three of those affected. Only 40% reported a cough or fever, which were the initial official symptoms that everyone was told to look out for.
The other key finding was that 98% of the survey respondents reported that their symptoms were mild to moderate, so they were more likely to continue with their daily activities.
Being more aware of symptoms is crucial so that when recognised, those experiencing them self-isolate. This is particularly important for healthcare workers in order to reduce the spread in hospitals.
How many infections were preventable?
We can never know the true number of healthcare workers who experienced smell loss and didn’t isolate that passed the virus to their co-workers or to other patients. But if nearly half of them continued to work, then we might estimate that over 5,000 healthcare workers per day were transmitting the virus in hospitals and to their families. We can only wonder at how many infections were preventable had these NHS staff members been warned about smell loss.
But this lesson applies to all of us. As the number of people affected by COVID increases and the information on patterns of symptoms increases, we must continue to stay alert to these symptom patterns and take appropriate action so that the virus can be contained until a safe, effective vaccine becomes available.
Smell loss has been a symptom that has long been neglected due to being thought of as unimportant. Hopefully, now it will be held with greater importance.
While 85% of those affected by smell loss were only without it for two to three weeks, an estimated 20,000 are still affected and adding to the 5% of the population for whom total smell loss is a daily fact of life.
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