Since the beginning of 2020, the COVID-19 pandemic has challenged healthcare and dramatically changed daily life for people worldwide. The severity of symptoms experienced by patients during the acute infection phase of COVID-19 disease varies between individuals from mild to severe. After this phase, there are usually no indications that the disease will have any long-term effects on their health, regardless of the severity of symptoms experienced during the acute infection phase. However, some patients continue to exhibit symptoms for prolonged periods after the acute phase. The symptoms experienced by such patients are broad, but can include, for example, deep fatigue, joint pain, ‘brain fog’ (difficulty concentrating on certain tasks for longer periods of time), and heart palpitations (Brodin, 2021, Marx, 2021). These symptoms can have a significant impact on the patients’ quality of life.

Most studies that have explored what causes some patients to experience prolonged symptoms have been descriptive. However, several recent studies have explored potential causes in detail. For example, Važgėlienė et al. (2022) investigated potential links between prolonged symptoms after COVID-19 infection and other types of chronic disease or daily medication. They found an association between the taking of daily medication and the development of prolonged symptoms after COVID-19 infection. Other studies have found that multiple other factors, including being female, advanced age, and poor general health, are associated with an increased risk of experiencing prolonged symptoms after a COVID-19 infection (Sudre et al., 2021).

This condition (i.e. the presistance of symptoms following the acute phase of COVID-19 infection) has been referred to in multiple ways, including Post COVID-19 condition, Post-COVID, and Long COVID. On this page, we use the term Post COVID-19 condition for consistency. See the Background Information section below for more detail about the nomenclature used and relevant research.

On this page, you can find visualisations of data related to Post COVID-19 condition in Sweden from The Swedish Board of Health and Welfare (Socialstyrelsen), an overview of ongoing Post COVID-19 condition research projects in Sweden, and scientific publications regarding Post COVID-19 condition by researchers affiliated with Swedish universities or research institutes.

For more information on Post COVID-19 condition in Sweden, please see this section of The Swedish Board of Health and Welfare (Socialstyrelsen)’s website and their report on Post-COVID condition (published April 2021). More general information is also available from the Centers for Disease Control and Prevention (CDC).

Availability of data and code

Data

The data underlying the visualisations on this page are from The Swedish Board of Health and Welfare and comprise of data from both the Patient Register and the ‘Cause of Death’ Register. The data are updated monthly, on the second Wednesday of the month, and are available for download here. Additional data about COVID-19 can be requested from the corresponding registers by any researchers fulfilling the requirements for access, the guidelines for access via the RUT (Register Utiliser Tool) are available here.

Code

All code used to produce the visualisations on this page is available on GitHub. The particular scripts used in each case are linked below the individual visualisations.

Statistics on Post COVID-19 condition in Sweden

Since Post COVID-19 condition is not clearly defined, over time, it has been assigned multiple diagnosis codes for use by medical professionals/researchers. After the first cases of prolonged disease following COVID-19 infection were detected in spring 2020, The Swedish Board of Health and Welfare initiated the diagnosis Z86.1A - COVID-19 in own medical history (Covid-19 i den egna sjukhistorien). This diagnosis code has been used since 1st June 2020. From 1st January 2021, this diagnosis code was replaced by U08.9 (ICD-10-SE) - COVID-19 in own medical history, unspecified (Covid-19 i den egna sjukhistorien) in accordance with new WHO (World Health Organization) guidelines. This diagnosis should be used when an individual is receiving treatment for an illness/physical damage for which the patient’s history of COVID-19 infection is considered relevant (i.e. a contributory factor to the present illness/damage). Importantly, this diagnosis should only be given if the individual is no longer considered to have COVID-19, and if the current health condition is not considered to result from infection with COVID-19. U08.9 is an additional diagnosis, as such, it should only be assigned alongside a main diagnosis; it cannot be the main diagnosis.

From 16th October 2020, the Swedish Board of Health and Welfare initiated a new diagnosis, U09.9 (ICD-10-SE) - Postinfectious state associated with COVID-19, unspecified (Postinfektiöst tillstånd efter covid-19, ospecificerat), in accordance with new WHO guidelines. This new diagnosis supplemented and partially replaced the Z86.1A diagnosis. As with U08.9, the U09.9 diagnosis should only be given after the person is no longer considered to have COVID-19. This diagnosis code should be used for conditions that persist or begin after the acute infection stage has passed. U09.9 is also an additional diagnosis, and should only be assigned alongside a separate main diagnosis.

For more information and current guidelines regarding diagnoses used for conditions related to a history of COVID-19, see this webpage from The Swedish Board of Health and Welfare.

Age and sex distribution of diagnosed cases

These plots display the number of times that patients were assigned the diagnoses of interest in Sweden since the introduction of the relevant codes, divided by patient age and sex.

Diagnosis U09.9

Code used to produce plot: Script to produce plot.

Diagnosis Z86.1A/U08.9

Code used to produce plot: Script to produce plot.

Geographic distribution of diagnosed cases relative to population size

The maps below show the number of people that received the diagnoses of interest in each county as a percentage of the total population of that county. The total population of the county and the number of people who received the diagnosis can be seen by hovering the mouse above a particular county.

Diagnosis U09.9

Code used to produce plot: Data preparation script, Script to produce map.

Diagnosis Z86.1A/U08.9

Code used to produce plot: Data preparation script, Script to produce map.

Most common accompanying diagnoses

Diagnosis U09.9

The below table displays the most common types of diagnosis (diagnosis groups) that have been reported together with the U09.9 (ICD-10-SE) - Postinfectious state associated with COVID-19, unspecified diagnosis. In particular, the values in the table represent the amount of individuals that received the U09.9 diagnosis alongside one of the diagnoses below. The data was recorded between 16th October 2020 and the most recent data update (see above).

Note that an individual may have more than one of the accompanying diagnoses. However, if an individual has the same issue on multiple doctor visits/healthcare contacts, the diagnosis will only be counted once

Code used to produce table: Script to produce table (English), Script to produce table (Swedish).

Contacts with healthcare

The below plot shows the number of times that patients given the diagnoses of interest have sought healthcare. Note that while the weekly data below starts from week 21 of 2020, some diagnosis codes (U08.9 and U09.9) were not used until after this date (see information above). It is important to note that the data is not complete, given that data from some healthcare providers (e.g. general practitioners) are not reported to the Patient Registry due to privacy concerns. Where data is reported to registers, data from the most recent weeks should be considered preliminary, as the registers are not instantaneously updated. A delay in reporting data to registers may be particularly evident during traditional holiday periods, including over the summer months.

Code used to produce plot: Script to produce plot.

Contacts with healthcare, divided by patient sex

The below plots show the number of times that patients given one of the diagnoses of interest have sought healthcare. The weekly number of healthcare visits is shown, divided by patient sex. As in the above section, it is important to note that the data is not complete, given that data from some healthcare providers (e.g. general practitioners) are not reported to the Patient Registry due to privacy concerns. Where data is reported to registers, data from the most recent weeks should be considered preliminary, as the registers are not instantaneously updated. A delay in reporting data to registers may be particularly evident during traditional holiday periods, including over the summer months.

Diagnosis U09.9

Code used to produce plot: Script to produce plot.

Diagnosis Z86.1A/U08.9

Code used to produce plot: Script to produce plot.

Ongoing research projects

Below is a manually curated overview of research projects on Post COVID-19 condition that are funded by major funding agencies in Sweden. As it is manually curated, the list may not be exhaustive and new projects will be added as soon as possible. If you think that your project should be listed here but isn’t, please get in touch with us. For a list of all research projects funded by major funding agencies in Sweden see this section of the portal.

Publications

Below is a list of pre-prints and published scientific journal articles on Post COVID-19 condition involving at least one author affiliated with a Swedish university or research institute. Note that this list is based on a manually curated database and, as such, may not be exhaustive. If you think that a publication should be listed here but isn’t, or feel that information about a publication needs correction, please get in touch with us. For a list of all publications on COVID-19 and SARS-CoV-2 involving at least one author affiliated with a Swedish univerisity or research institute see this section of the portal.

Background Information

Post COVID-19 condition

Individuals with Post COVID-19 condition exhibit symptoms lasting at least two months after the acute phase of COVID-19 infection (Brodin, 2021). The particular symptoms exhibited vary between patients, as does the duration and severity of symptoms. In general though, symptoms are usually debilitating and may include persistent fatigue, myalgia (muscle aches and pains), and autonomic dysregulation, among others. Some individuals with Post COVID-19 condition exhibit the same symptoms as they did during the acute infection stage of COVID-19, while others with Post COVID-19 condition exhibit new symptoms following the acute infection phase (Brodin 2021, Dennis et al., 2021, Davido et al., 2020.

No consensus on definition

In September 2020, WHO established the ICD10 code for Post COVID-19 condition U09.9 - Post COVID-19 condition, unspecified. A WHO report from April 2021 stated that there is a real need to characterise and formally define Post COVID-19 condition in order to increase understanding about the condition and facilitate diagnosis. However, to date, Post COVID-19 condition still lacks a universal definition with regard to the symptoms and disease duration necessary for diagnosis. Consequently, governmental agencies and research institutes in different countries use their own definitions and terms. Related diagnoses established by WHO are U08.9 - Personal history of COVID-19, unspecified and U10.9 - Multisystem inflammatory syndrome associated with COVID-19, unspecified. The U08.9 diagnosis is used to describe an earlier episode of COVID-19 (either confirmed or probable) that influenced the individual’s health status, though they no longer have COVID-19. The code U10.9 is used to describe a temporal association with COVID-19: cytokine storm, Kawasaki-like syndrome, multisystem inflammatory syndrome in children (MIS-C), and paediatric inflammatory multisystem syndrome (PIMS).

In England, the National Institute for Health and Care Excellence (NICE) has defined Post-COVID-19 syndrome as “…signs and symptoms that develop during or after an infection consistent with COVID‑19, continue for more than 12 weeks, and are not explained by an alternative diagnosis. It usually presents with clusters of symptoms, often overlapping, which can fluctuate and change over time and can affect any system in the body…”. NICE states that Post‑COVID‑19 syndrome can be considered as a diagnosis during the first three months after the acute infection phase of COVID-19 while healthcare assessments are completed to determine whether the symptoms could be explained by an alternative disease. Further, NICE defines the term Long COVID as “…signs and symptoms that continue or develop after acute COVID‑19. It includes both ongoing symptomatic COVID‑19 (from 4 to 12 weeks) and post‑COVID‑19 syndrome (12 weeks or more)…”. In December 2020, NICE, in partnership with the Scottish Intercollegiate Guidelines Network and the Royal College of General Practitioners, published a guideline for health and care practitioners (NG188) on identifying, assessing, and managing the long-term effects of COVID-19.

In the USA, The Centers for Disease Control and Prevention (CDC) defines Post-COVID conditions as “…a wide range of new, returning, or ongoing health problems people can experience more than four weeks after first being infected with the virus that causes COVID-19…”. The CDC distinguishes between Long COVID, Multiorgan Effects of COVID-19, and Effects of COVID-19 Treatment or Hospitalisation. For example, they define Long COVID as “a range of symptoms that can last weeks or months after first being infected with the virus that causes COVID-19 or can appear weeks after infection.”. For information on Post-COVID conditions from the CDC, see this page. The National Institutes of Health (NIH) in the USA uses the term Post-Acute Sequelae of SARS-CoV-2 infection (PASC) to refer to the effects of COVID-19 after the initial stages of infection. In February 2021, The NIH launched a research initiative to identify the causes of PASC and, ultimately, to find methods for prevention and treatments for individuals that don’t recover fully over a period of a few weeks following the acute infection phase of COVID-19.

The Swedish Board of Health and Welfare (Socialstyrelsen) describes patients with Postcovid as individuals exhibiting prolonged symptoms, or experiencing new relevant symptoms after the acute phase of COVID-19 infection. While the severity of symptoms will diminish over time for most individuals (such individuals do not need assistance from healthcare during the recovery), some individuals experience symptoms that are debilitating and need treatment, rehabilitation, and other follow-up medical care. In April 2021, Socialstyrelsen published a report dedicated to Postcovid that defines the condition and provides recommendations.

Research efforts

A large number of research articles, case reports, and reviews focused on Post COVID-19 condition have been published over the last year (e.g. Dani et al. (2020), Nabavi (2020), Sudre et al. (2021), Tarybagil et al. (2020), Yelin et al. (2020)). The primary aims of these studies are to identify factors that could be used to predict when Post COVID-19 condition is more likely to develop, the underlying causes of the condition, and potential treatments. A recently published study by Sudre and colleagues proposed a prediction model to identify individuals at risk of Post COVID-19 condition using data from the COVID Symptom Study, where participants self-reported their symptoms in an app on their mobile devices. The results indicated that individuals experiencing more than five symptoms during the first week of illness were more likely to develop Post COVID-19 condition (odds ratio = 3.53 (2.76–4.50)). In addition, the study showed that the development of Post COVID-19 condition was more likely in females, and that the risk also rose with increasing age and body mass index. The researchers behind the study propose that their model could be used to identify individuals at risk of developing Post COVID-19 condition. This could inform trials of preventative or treatment methods, and aid in the planning of education and rehabilitation services.