COVID-19 for health professionals: Post COVID-19 condition (long COVID)
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About the condition
The World Health Organization (WHO) defines post COVID-19 condition as:
“[…] occurring in individuals with a history of probable or confirmed SARS CoV-2 infection, usually 3 months from the onset of COVID-19 with symptoms and that last for at least 2 months and cannot be explained by an alternative diagnosis. Common symptoms include fatigue, shortness of breath, cognitive dysfunction but also others and generally have an impact on everyday functioning. Symptoms may be new onset following initial recovery from an acute COVID-19 episode or persist from the initial illness. Symptoms may also fluctuate or relapse over time.”
Some studies have reported long-term symptoms in patients with a severe COVID-19 infection. For example, those who were hospitalized or needed intensive care during recovery. However, post COVID-19 condition may also occur in people with mild or asymptomatic infection.
Given the limited availability of testing capacity early in the pandemic, there are patients experiencing post COVID-19 condition symptoms who were not formally tested and diagnosed with COVID-19.
Currently, the estimates on how often people experience post COVID-19 condition are inconsistent. This is due to differences in:
- how symptoms are measured
- what symptoms are examined
- the number of participants in the study
- the length of time the patients were followed
- which populations are included in the study (hospitalized versus outpatient versus undiagnosed or asymptomatic)
Post COVID-19 condition is associated with a wide range of diverse symptoms across multiple organ systems. Symptoms can fluctuate in intensity, and can sometimes disappear and reappear. Some patients report that mental and physical over-exertion may exacerbate the condition.
The Public Health Agency of Canada (PHAC) recently released a review of the current international evidence (PDF). Over 100 symptoms or difficulties conducting usual activities of daily living were reported. Findings from this review (peer-reviewed studies published up to April 2021) and from a recent peer-reviewed study found the proportion to be 30% to 40% in individuals who were not hospitalized for their initial COVID-19 infection. Current evidence suggests that the prevalence is higher among those who were hospitalized during the acute phase compared to those who were not hospitalized. These estimates are likely to change in the future as the results of additional studies become available.
Post COVID-19 condition typically appears in adult patients. However, emerging evidence shows that children may also develop chronic, persisting symptoms after COVID-19 infection. There is still a lot that we don’t know about post COVID-19 condition in children. The prevalence of this condition in children is not yet well established, with high variability in estimates being observed from only a small number of studies. These estimates will become more precise as more studies are conducted and new evidence emerges.More research is needed on the longer-term symptoms after a COVID-19 infection in children and adolescents.
Mental health symptoms, such as anxiety and depression, are commonly reported by individuals experiencing post COVID-19 condition. Patients should be encouraged to talk to their health care provider if they think they may be experiencing symptoms of anxiety, depression or posttraumatic stress disorder. Wellness Together Canada is a resource for patients in crisis.
Prevention, diagnosis and treatment
Ongoing research about what causes post COVID-19 condition and how to diagnose and treat it will help develop specific supports tailored to patients. The WHO, along with patients, researchers and others, developed a clinical case definition of post COVID-19 condition. This will help both patients and clinicians during the diagnostic process. The WHO is also inviting clinicians and patients to collect information in a systematic way through a case report form for post COVID-19 condition. This will help to expand our knowledge on the condition, and better support patient care and public health interventions.
There is currently no universally agreed-upon approach to diagnose and treat post COVID-19 condition. Sources of knowledge and support about the management of symptoms include:
- patient-led research
- patient-led initiatives
- emerging research on models of care (PDF, updated December 2021)
- emerging guidelines from UK NICE (updated March 1, 2022) and the Centers for Disease Control and Prevention
- clinical resources for health professionals
- Post COVID-19 Condition (Ontario): Guidance for Primary Care (PDF)
Some preliminary findings also suggest that vaccination with 2 or more doses prior to getting infected with COVID-19 may help reduce the risk of developing post COVID-19 condition. PHAC continues to monitor new developments to learn more about other preventive measures that can be taken.
The provinces and territories are responsible for the management and delivery of health care services for their residents. This includes rehabilitation and treatment services for people with post COVID-19 condition. There are a number of public and private clinics that provide care to individuals with post COVID-19 condition across Canada, which have a clear focus on interdisciplinary care.
What Canada is doing
PHAC is reviewing published studies on post COVID-19 condition to identify:
- which symptoms are most common
- its associated risk factors
- how to prevent it
- how many individuals (adults and children) are having difficulties with regular activities and daily living
PHAC also collaborated with Statistics Canada on a new population-based Canadian COVID-19 Antibody and Health Survey (CCAHS) launched in April 2022. The survey was sent to 100,000 randomly selected Canadians aged 18 years and older across the 10 provinces, and will be used to:
- estimate the percentage of Canadian adults who are living with post COVID-19 condition
- provide information on symptoms, including severity, duration and impact on daily activities
- identify risk factors associated with developing post COVID-19 condition
Provisional results from this survey provide valuable insight on the burden of longer-term COVID-19 symptoms in Canadian adults aged 18 years and older. The new results presented are in line with results from other surveys and evidence internationally.
This data blog is the first in a suite of products related to this survey planned for winter and spring 2023 to further our knowledge about longer-term COVID-19 symptoms.
PHAC continues to:
- gather evidence about how common these long-term effects are in Canada
- work with partners to explore the development and implementation of other public health surveillance activities to examine post COVID-19 condition
- these partners include:
- Statistics Canada
- the provinces and territories
- academic and professional organizations
- these partners include:
We are also working with other partners to gather evidence to support our research, like the:
- Canadian Institutes of Health Research
- Canadian Institute for Health Information
For more resources and links to knowledge products, data and evidence on the impacts of COVID-19, which includes post COVID-19 condition, visit the COVID-19 virtual library of health data and evidence. This is a searchable collection of products funded and published by the Government of Canada.
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