Nisreen A Alwan: What exactly is mild covid-19? 

We still know very little about covid-19, but we do know that we cannot fight what we do not measure

It is the morning after. I went out for a 20 minute slow walk yesterday evening with my little girl who was desperate to see the flowers on the way. My exercise capacity is still terrible, and I knew that by doing that I would pay the price the day after. Indeed, I woke up with the familiar chest heaviness and utter exhaustion which gets worse by sitting at my desk to work.

This has been a pattern since the start of my covid-19 symptoms in the second half of March. Of course, I was never tested because community testing stopped altogether in the UK on the 12 March so I have no proof of my infection other than the accounts of thousands of people who are describing a similar experience of prolonged, fluctuating, and debilitating symptoms lasting for months. We are the unrecorded. The pandemic has been measured in deaths and in hospital admissions. I struggle to find any precise case definition for “mild” covid-19, which is what I supposedly had and still have not fully recovered from. 

It seems common in many countries that anyone with symptoms, but not hospitalised is counted as a “mild” case, but the degree of covid-19 severity must be defined by the duration of ill health, not just the need for hospital admission. If symptoms last for more than a month and are debilitating to usual activities, it is unreasonable to call this a “mild” case. This misconception of “mild” is not ideal for prevention efforts during the pandemic. The infection is still depicted to the population as only affecting the elderly and those with a chronic condition, while “healthy” people would have no or brief symptoms if they get it. Evidence is emerging that for a significant proportion of those infected this is not true. A Dutch survey of more than 1,600 covid-19 patients, 91% of which were not hospitalised and 85% described their health as good before the infection, found that symptoms such as fatigue (88%), shortness of breath (75%), chest pressure (45%), headache (40%), muscle pain (36%) and palpitations (32%) last for months after initial infection. Nearly half of those surveyed said they were no longer able to exercise. The UK COVID Symptom Study App found that 10% of people reporting symptoms are sick for more than three weeks.

There are huge productivity implications for prolonged ill health following initial SARS-CoV-2 infection. Many doctors have been unable to recover and work for several weeks. These are largely the young and healthy who were expected to shake the infection off like a common cold and bounce back to work and caring duties within a few days. There are 12,900 members of the Long Covid Facebook group and over 14,000 members of The Body Politic Slack-channel covid-19 support group. Countries that adopted a laissez faire attitude towards the pandemic by accepting or even encouraging the virus to run through society while only protecting the vulnerable did not bear in mind this possibility. Herd immunity through natural infection should have never been a viable strategy to explore with a new virus that we had no knowledge about its health consequences on a population level. We still do not even know exactly who are “the vulnerable” in order to protect them, not only in terms of mortality, but in terms of moderate to long-term health outcomes.

As a public health doctor and epidemiologist, I strongly think we must now clearly define and measure “recovery” from covid-19. This way we can quantify non-death health outcomes and monitor long-term implications of the virus. The definition needs to be more sophisticated than just hospital discharge or testing negative for the virus. It must take into account symptom duration, fluctuation, overall functionality and quality of life in comparison to before infection. If we do not have enough information to define “mild” at this stage, then let us not use the term loosely, otherwise it is detrimental to pandemic control.

What is now becoming clear is that mortality is not the only adverse outcome of this infection and our surveillance systems must keep up and reflect that. I am advocating for precise case definitions for covid-19 morbidity that reflect the degree of severity of infection and allow us to measure moderate and long term health and wellbeing outcomes. At this stage of the pandemic, it is vital that we accurately measure and count all degrees of infection, not only in research cohorts, but as part of population-based routine surveillance systems. This includes people like me who were not tested at the time of their initial infection. Death is not the only thing to count in this pandemic, we must count lives changed. We still know very little about covid-19, but we do know that we cannot fight what we do not measure. 

Nisreen A Alwan is an Associate Professor in Public Health at the University of Southampton and an Honorary Consultant of Public Health at University Hospital Southampton NHS Foundation Trust. @Dr2NisreenAlwan 

Competing interests: None declared