By Sarah Garland

There are lots of names for it. Long COVID and post-COVID-19 condition are the most common. It’s an emerging issue that some people with COVID-19, whether or not they had symptoms initially, can develop symptoms that last weeks or months after their initial illness. In the beginning days of the pandemic, most thought that COVID-19 was a short-term, acute illness, and most people would recover in a few weeks. However, it soon became apparent that some individuals were experiencing symptoms long after they first were diagnosed.

CADTH (an independent agency that finds, assesses, and summarizes the research on drugs, medical devices, tests, and procedures) recently published a report on what is currently known about long COVID condition. This report looks at what is known about long COVID, emerging research questions, and implications for the health care system.

There’s a lot of uncertainty about long COVID, but it’s clear that this condition could have profound impact on health care systems. Recent estimates suggest that 150,000 Canadians may be affected by long COVID (based on a June 2021 report by SPOR Evidence Alliance and the COVID-END Network). Though it’s hard to know exactly how many people will develop long COVID — and estimates of current prevalence vary widely — worldwide, long COVID is estimated to affect millions of people.

Part of the variability relates to whether the initial COVID-19 infection was confirmed or was suspected (i.e., an individual’s symptoms suggested they likely had COVID-19). In the earlier days of the pandemic, access to testing was limited, and so not everyone with COVID-19 had a positive test to confirm their illness. The World Health Organization (WHO), in their October 2021 definition of long COVID, acknowledge this variability in testing, stating that the definition includes individuals with probable, as well as those with confirmed, COVID-19 infection.

Timelines for defining what constitutes long COVID also vary. But, according to the WHO definition, it’s when a person is thought to have had COVID-19 for (usually) 3 months with symptoms lasting for at least 2 months that can’t be explained by an alternative diagnosis. There is some variation in this too – people may have recovered from their initial illness, and then symptoms return, or they have new symptoms. When suspected and confirmed COVID-19 cases are combined, current estimates suggest that 21% to 23% of people have symptoms 4 weeks after being infected with COVID, and 14% have symptoms 12 weeks after their initial illness.

Like acute COVID-19 condition (typically considered to last for up to 4 weeks after infection), there’s a variety of symptoms associated with long COVID. In part, this is because COVID-19 can impact multiple organs in the body. Some common symptoms are fatigue, fever, breathlessness, cough, and chest pain. As well, some may experience “brain fog” (or the inability to think clearly), headache, dizziness, and sleep disturbances. Other symptoms may be gastrointestinal pain (e.g., stomach pain); joint and muscle pain; psychological symptoms (e.g., depression); ear, nose, and throat symptoms (e.g., loss of taste and smell, ringing in their ears); and skin issues (e.g., rash). To complicate things further, an individual’s symptoms may fluctuate over time, relapse, or be triggered. For example, some people may experience worse symptoms after exercising.

As far as treatment goes, current recommendations focus on personalized care involving multiple clinical disciplines that reflect the complexity and variety of symptoms experienced by each patient. Possible components of treatment include self-management, such as education and support, and guidance for symptom specific management, like breathing exercises to improve shortness of breath.

There’s also variability in the treatment and management of long COVID. There are some specialized clinics dedicated to long COVID patients, while other models of care centre on primary care providers referring patients to specialists as needed. There are also hybrid models that use a mix of post-COVID-19 clinics and primary care providers, depending on the needs of each patient.

Regardless of the model of care, long COVID could place demands on health care systems already struggling with the demands of the pandemic. For example, many people who suspect they have long COVID turn to their primary care providers, then to multidisciplinary specialists and rehabilitation services. To rule out other illnesses, they may need medical imaging and blood work. If they experience psychological symptoms of long COVID, they may access mental health treatments and supports. There are many ways the health care system is responding to the needs of individuals with long COVID, and it will take considerable time for us to realize the full impact of this condition. It should also be noted that long COVID has far reaching effects for individuals and may reduce their ability to fully participate in their daily lives, like going to school or work.

To summarize, long COVID is a complex condition with a large degree of variability among individuals. Right now, there is a lot of uncertainty about how best to prevent, treat, and manage long COVID. It will take time to develop a clear picture of post-COVID-19 condition and its full implications for health care systems.

To read the full report, you can access it — “An Overview of Post-COVID-19 Condition (Long COVID)” — in the 9th issue of the Canadian Journal of Health Technologies. Visit CADTH’s YouTube page (https://www.youtube.com/user/CADTHACMTS) to view a panel of experts discussing the implications of long COVID. To find out more about CADTH, visit cadth.ca, follow CADTH on Twitter: @CADTH_ACMTS, or talk to our Liaison Officer in your region: cadth.ca/contact-us/liaison-officers.

Sarah Garland is a knowledge mobilization officer at CADTH.