Long COVID

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Long COVID logo with Coronavirus icon

Long COVID, long tail covid, Post-Acute Sequelae of COVID-19 (PASC), post-acute COVID-19 and ongoing COVID are terms used to describe a group of long term health problems that are found in a significant minority of people who developed COVID-19 and remain ill a number of weeks or months later.[1][2][3][4]

The name Long COVID was coined by patient Elisa Perego in May 2020,[5] and in February 2021 the CDC introduced the alternative name Post-Acute Sequelae of COVID-19 (PASC).[6]

In February 2020, the World Health Organization stated that the expected recovery time from COVID-19 was 2 weeks for mild cases, and between three and six weeks for severe cases;[7] follow-up studies then identified a significant number of COVID-19 patients had remained ill much longer than this: those with long COVID.[1][2]

A similar phenomenon to long COVID occurred after the 2003 outbreak of the similar SARS coronavirus, which lead to a post-SARS syndrome being proposed that included chronic widespread musculoskeletal pain, fatigue, depression and disordered sleep. Another study found a subgroup SARS survivors developed chronic fatigue syndrome immediately after SARS.[8] [9]

Long-haulers[edit | edit source]

A "long-hauler" is someone with long COVID, meaning someone who became ill with confirmed or suspected COVID-19, who has remained ill with long-term symptoms many weeks or months later after first becoming ill.[3][5]

What is long COVID[edit | edit source]

Long COVID poster - 1 in 10 people with COVID-19 may develop long COVID

Long COVID appears to be a multisystem disease, and may occur after any severity of COVID-19, including after relatively mild cases.[2][5]

Signs and symptoms[edit | edit source]

Patient surveys have reported that the following symptoms commonly occur in long COVID.

Other reported symptoms include:

“A very common feature is the relapsing, remitting nature of the illness, where you feel as though you’ve recovered, then it hits you back

“
”
Dr. Nisreen Alwan, BMJ, Sep 2020


World Health Organization Long COVID diagnostic criteria[edit | edit source]

Post COVID-19 condition ("Long COVID") definition

  • history of probable or confirmed SARS-CoV-2 infection
  • symptom(s) last 2 months from the start of COVID-19 (or 3 months for asymptomatic COVID-19)
  • symptom(s) can't be explained by an alternative diagnosis
  • no minimum number of symptoms
  • symptom(s) generally affect day to day functioning
  • new onset of symptoms - symptoms begin after recovery from COVID-19 or begin at the start of COVID-19 and persist
  • symptoms can fluctuate or improve then relapse over time

Common symptoms:

Other symptoms:


Notes:

  • Children - separate criteria may be needed
  • Clusters - clusters of 2 or more related symptoms may occur together[16]
See also
World Health Organization Long COVID diagnostic criteria.

Four different syndromes[edit | edit source]

A recent review suggested that long COVID may actually be four differing syndromes:

Patients with long COVID may have several syndromes at once.[17]

COVID-19 testing[edit | edit source]

While some people with long COVID did have a positive test result for COVID-19, others were denied tests due to the limited availability of tests at the time, or they tested negative but were found to have clear evidence of COVID-19 from blood count tests or chest X-rays.[17][18] Some people with Long COVID have described never having a cough or fever at the start of their illness, but developed these symptoms later. Long COVID diagnosis does not depend on a previous positive test.[17][18]

Clinical findings[edit | edit source]

There is no blood test or diagnostic biomarker to identify patients with long COVID. A study of UK patients by Dennis et al (2020) found that just over 10% of long COVID patients had abnormal findings on the standard tests and did not find an association between standard test results and degree of organ damage or long COVID severity.[19] The same study used MRI scans combined with patient questionnaires to assess organ damage, finding that multi-organ impairment was common in people with long COVID, despite the fact that 80% had not been hospitalized for COVID-19, the average patient age was forty-four years old, and rates of pre-existing conditions were also low.[19]

Research findings[edit | edit source]

Main article: Long COVID pathophysiology

Surveys of data collected and published by long haulers using social media were the first evidence of what symptoms and health problems were caused by long COVID.[20] Later academic studies confirmed many of the initial long hauler survey findings, although many only involved patients discharged from hospital,[21] patients who had been able to access early testing and tested positive, or patients who had sought medical care in a particular location.[22] People with mild COVID-19 symptoms, leaving people denied testing and those who may have had false negative test results and people who tested positive but were asymptomatic underrepresented in long COVID research.[20]

Treatment[edit | edit source]

Pacing[edit | edit source]

Pacing is a method of activity management which aims to adapt everday activities in order to avoid relapses or increased symptoms.

See also
Pacing.

Exercise therapy[edit | edit source]

ME/CFS patient groups have raised concerns about the use of graded exercise therapy (GET) in long COVID patients and a similar warning has been issued by NICE in the UK.[23] Graded exercise therapy, which is sometimes incorrectly referred to as "activity management" involves patients initially reducing their activity levels to a level that prevents regular crashes, and then typically increasing activity by 10% each week regardless of any increased symptoms or worsening illness. In graded exercise patients are told to ignore deterioration or increased symptoms and "push through" them.

Theory and evidence[edit | edit source]

In graded exercise therapy patients are told that their symptoms are caused only by inactivity and other "bad habits" rather than an underlying illness. These assumptions have very weak evidence, and significant evidence exists of underlying illness in ME/CFS; there is a lack of research about exercise therapy for long COVID illness[1] but some symptoms are inconsistent with this "deconditioning" assumption and some research has found physical abnormalities in some patients weeks or month after infection. Surveys of ME/CFS patients have consistently shown that large numbers of patients deteriorate as a result of graded exercise therapy, and a significant number become severely ill and never return to the level of functioning they had before the treatment.

ME/CFS[edit | edit source]

Postviral fatigue syndrome is one of the previous names used for Myalgic Encephalomyelitis (ME), sometimes known as Chronic Fatigue Syndrome (CFS), and it commonly begins immediately after events such as a virus, bacterial or other infection.[24] ME has been a sequela of over one hundred outbreaks, in addition to sporadic infections. ME/CFS is not normally diagnosed until symptoms have persisted for six months or more, and tests must be run to exclude other possible causes of the symptoms.[25] Some contagious diseases including Epstein-Barr virus, certain enteroviruses,[24] and the SARS coronavirus,[8] have caused outbreaks of ME/CFS. It is not yet known how likely it is for ME/CFS to begin immediately after COVID-19 illness, although around 10% people with certain viruses are known to develop ME/CFS, and according to the BMJ around 10% of people with COVID-19 have developed long COVID. A significant number of those with long COVID have been found to develop ME/CFS, but it is not known how common this is.[2][17]

According to infectious diseases and immunology researcher, Sonya Marshall-Gradisnik, there appeared to be a correlation between the illnesses.

"The symptom overlap between ME/CFS and long-COVID is quite astounding," Professor Marshall-Gradisnik said.Those symptoms can be fatigue, they have pain, joint pain, sleep disturbances, headaches, they have cardiac changes. Notably, they've got brain fog and cognitive issues with memory, [and] word choice becomes a problem."[26]

Patient surveys[edit | edit source]

Not peer reviewed

Data collected: Apr 21 - May 2 2020. Respondents: 640
Data collected: Jul 25, 2020. Respondents: 1,567+

Notable studies[edit | edit source]

  • Jul 24, 2020, Outcomes of Cardiovascular Magnetic Resonance Imaging in Patients Recently Recovered From Coronavirus Disease 2019 (COVID-19)[21] - (Full text)
  • Aug 11, 2020, Management of post-acute covid-19 in primary care[2] - (Full text)
  • Aug 20, 2020, New-Onset Diabetes in Covid-19[11] - (Full text)
  • Oct 1, 2020, Long-term consequences of COVID-19: research needs[14] - (Full text)
  • Oct 14, 2020, Finding the 'right' GP: a qualitative study of the experiences of people with long-COVID[18] - (Full text)
  • Oct 16, 2020, Multi-organ impairment in low-risk individuals with long COVID[19] - (Full text)
  • Oct 21, 2020, Attributes and predictors of Long-COVID: analysis of COVID cases and their symptoms collected by the Covid Symptoms Study App[27] - (Full text)
  • Dec 2020 (pre-print) / Jul 15, 2021, Characterizing long COVID in an international cohort: 7 months of symptoms and their impact[10] - (Abstract)
  • Dec 2020, Long COVID-19: Challenges in the diagnosis and proposed diagnostic criteria[28] (Full text)
  • Dec 20, 2020, Patient outcomes after hospitalisation with COVID-19 and implications for follow-up; results from a prospective UK cohort[22] - (Full text) - from the DISCOVER project
  • Jan 18, 2021, Will COVID-19 lead to myalgic encephalomyelitis/chronic fatigue syndrome?[29] - (Full text)
  • Mar 27, 2021, COVID-19 Survivors’ Reports of the Timing, Duration, and Health Impacts of Post-Acute Sequelae of SARS-CoV-2 (PASC) Infection[30] - (Full text)
  • May 11, 2021, Mayo Clinic Proceedings: Post COVID-19 Syndrome (Long Haul Syndrome): Description of a Multidisciplinary Clinic at the Mayo Clinic and Characteristics of the Initial Patient Cohort[31] - (Abstract)
  • Jun 7, 2021, Insights from ME/CFS May Help Unravel the Pathogenesis of Post-Acute COVID-19 Syndrome[32] - (Full text)
  • Jun 23, 2021, Long COVID or Post-acute Sequelae of COVID-19 (PASC): An Overview of Biological Factors That May Contribute to Persistent Symptoms[33] - (Full text)
  • Oct 2021, A clinical case definition of post COVID-19 condition by a Delphi consensus[16] (Full text)
  • Feb 2024, Blood–brain barrier disruption and sustained systemic inflammation in individuals with long COVID-associated cognitive impairment[34]
Report including the World Health Organization Long COVID diagnostic criteria

Articles and editorials[edit | edit source]

  • Jun 15, 2021, White Paper: A Detailed Study of Patients with Long-Haul COVID[35] (Full text)
  • Jun 24, 2021, Covid-19: Third of people infected have long term symptoms[36] (Editorial)

Presentations, interviews and videos[edit | edit source]

Letters and blogs[edit | edit source]

National and international health bodies[edit | edit source]

News articles[edit | edit source]

Articles for journalists covering Long COVID[edit | edit source]

See also[edit | edit source]

Learn more[edit | edit source]

References[edit | edit source]

  1. ↑ 1.0 1.1 1.2 1.3 Nabavi, Nikki (September 7, 2020). "Long covid: How to define it and how to manage it". The BMJ. 370: bmj.m3489.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Greenhalgh, Trisha; Knight, Matthew; A'Court, Christine; Buxton, Maria; Husain, Laiba (August 11, 2020). "Management of post-acute covid-19 in primary care". The BMJ. 370: m3026. doi:10.1136/bmj.m3026.
  3. ↑ 3.0 3.1 Yong, Ed (August 19, 2020). "Long-Haulers Are Redefining COVID-19". The Atlantic. ISSN 1072-7825. Retrieved August 21, 2020.
  4. ↑ National Institute for Health Research. "Living with COVID: NIHR publishes dynamic themed review into 'ongoing COVID'". National Institute for Health Research. Retrieved October 15, 2020.
  5. ↑ 5.0 5.1 5.2 Perego, Elisa; Callard, Felicity; Stras, Laurie; Melville-Jóhannesson, Barbara; Pope, Rachel; Alwan, Nisreen A (October 1, 2020). "Why we need to keep using the patient made term "Long Covid"". The BMJ. Retrieved October 11, 2020.
  6. ↑ Collins, Francis (January 19, 2021). "Trying to Make Sense of Long COVID Syndrome". Retrieved March 1, 2021.
  7. ↑ World Health Organization (February 24, 2020). "WHO Director-General's opening remarks at the media briefing on COVID-19". World Health Organization. Retrieved September 24, 2020.
  8. ↑ 8.0 8.1 Moldofsky, Harvey; Patcai, John (March 24, 2011). "Chronic widespread musculoskeletal pain, fatigue, depression and disordered sleep in chronic post-SARS syndrome; a case-controlled study". BMC Neurology. 11 (1): 37. doi:10.1186/1471-2377-11-37. ISSN 1471-2377. PMC 3071317. PMID 21435231.
  9. ↑ Lam, Marco Ho-Bun; Wing, Yun-Kwok; Yu, Mandy Wai-Man; Leung, Chi-Ming; Ma, Ronald C.W.; Kong, Alice P.S.; So, W.Y.; Fong, Samson Yat-Yuk; Lam, Siu-Ping (December 14, 2009). "Mental Morbidities and Chronic Fatigue in Severe Acute Respiratory Syndrome Survivors: Long-term Follow-up". Archives of Internal Medicine. 169 (22): 2142–2147. doi:10.1001/archinternmed.2009.384. ISSN 0003-9926.
  10. ↑ 10.0 10.1 Davis, Hannah E.; Assaf, Gina S.; McCorkell, Lisa; Wei, Hannah; Low, Ryan J.; Re'em, Yochai; Redfield, Signe; Austin, Jared P.; Akrami, Athena (July 15, 2021). "Characterizing long COVID in an international cohort: 7 months of symptoms and their impact". EClinicalMedicine. 38: 101019. doi:10.1016/j.eclinm.2021.101019. ISSN 2589-5370. PMC 8280690. PMID 34308300.
  11. ↑ 11.0 11.1 Rubino, Francesco; Amiel, Stephanie A.; Zimmet, Paul; Alberti, George; Bornstein, Stefan; Eckel, Robert H.; Mingrone, Geltrude; Boehm, Bernhard; Cooper, Mark E. (August 20, 2020). "New-Onset Diabetes in Covid-19". New England Journal of Medicine. 383 (8): 789–790. doi:10.1056/NEJMc2018688. ISSN 0028-4793. PMC 7304415. PMID 32530585.
  12. ↑ 12.0 12.1 Lambert, Natalie J; Survivor Corps (July 2020). "COVID-19 "Long Hauler" Symptoms Survey Report" (PDF). Indiana University School of Medicine.
  13. ↑ National Health Service (September 7, 2020). "COVID-19 Long Term Health Effects".
  14. ↑ 14.0 14.1 Yelin, Dana; Wirtheim, Eytan; Vetter, Pauline; Kalil, Andre C.; Bruchfeld, Judith; Runold, Michael; Guaraldi, Giovanni; Mussini, Cristina; Gudiol, Carlota (October 1, 2020). "Long-term consequences of COVID-19: research needs". The Lancet Infectious Diseases. 20 (10): 1115–1117. doi:10.1016/S1473-3099(20)30701-5. ISSN 1473-3099. PMID 32888409.
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Davis2021
  16. ↑ 16.0 16.1 Soriano, Joan B.; Allan, Maya; Alsokhn, Carine; Alwan, Nisreen A.; Askie, Lisa; Davis, Hannah E.; Diaz, Janet V.; Dua, Tarun; de Groote, Wouter; Jakob, Robert; Lado, Marta; Marshall, John; Murthy, Srin; Preller, Jacobus; Relan, Pryanka; Schiess, Nicoline; Seahwag, Archana (October 6, 2021), A clinical case definition of post COVID-19 condition by a Delphi consensus, World Health Organization (WHO) clinical case definition working group on post COVID-19 condition, World Health Organization
  17. ↑ 17.0 17.1 17.2 17.3 NIHR (October 2020). "Living with covid-19. A dynamic review of the evidence around ongoing covid-19 symptoms (often called long covid)". evidence.nihr.ac.uk. Retrieved October 15, 2020.
  18. ↑ 18.0 18.1 18.2 Kingstone, Tom; Taylor, Anna K.; O'Donnell, Catherine A.; Atherton, Helen; Blane, David N.; Chew-Graham, Carolyn A. (October 14, 2020). "Finding the 'right' GP: a qualitative study of the experiences of people with long-COVID". BJGP Open. doi:10.3399/bjgpopen20X101143. ISSN 2398-3795. PMID 33051223.
  19. ↑ 19.0 19.1 19.2 Dennis, Andrea; Wamil, Malgorzata; Kapur, Sandeep; Alberts, Johann; Badley, Andrew D.; Decker, Gustav Anton; Rizza, Stacey A.; Banerjee, Rajarshi; Banerjee, Amitava (October 16, 2020). "Multi-organ impairment in low-risk individuals with long COVID". medRxiv: 2020.10.14.20212555. doi:10.1101/2020.10.14.20212555.
  20. ↑ 20.0 20.1 20.2 Assaf G, Davis H, McCorkell L, Wei H, O'Neil B, Akrami A, Low R, Mercier J, A A, L T, C A, S M, N L, H N, D JD, S (May 11, 2020). "What Does COVID-19 Recovery Actually Look Like? An Analysis of the Prolonged COVID-19 Symptoms Survey by Patient-Led Research Team".
  21. ↑ 21.0 21.1 Puntmann, Valentina O.; Carerj, M. Ludovica; Wieters, Imke; Fahim, Masia; Arendt, Christophe; Hoffmann, Jedrzej; Shchendrygina, Anastasia; Escher, Felicitas; Vasa-Nicotera, Mariuca (July 27, 2020). "Outcomes of Cardiovascular Magnetic Resonance Imaging in Patients Recently Recovered From Coronavirus Disease 2019 (COVID-19)". JAMA Cardiology. doi:10.1001/jamacardio.2020.3557. ISSN 2380-6583.
  22. ↑ 22.0 22.1 Arnold, David T.; Hamilton, Fergus W.; Milne, Alice; Morley, Anna J.; Viner, Jason; Attwood, Marie; Noel, Alan; Gunning, Samuel; Hatrick, Jessica (April 1, 2021). "Patient outcomes after hospitalisation with COVID-19 and implications for follow-up: results from a prospective UK cohort". Thorax. 76 (4): 399–401. doi:10.1136/thoraxjnl-2020-216086. ISSN 0040-6376. PMID 33273026.
  23. ↑ 23.0 23.1 Forward-ME (August 27, 2020). "Letter re Covid-19 Management and Exercise Caution" (PDF).
  24. ↑ 24.0 24.1 Carruthers, BM; van de Sande, MI; De Meirleir, KL; Klimas, NG; Broderick, G; Mitchell, T; Staines, D; Powles, ACP; Speight, N; Vallings, R; Bateman, L; Bell, DS; Carlo-Stella, N; Chia, J; Darragh, A; Gerken, A; Jo, D; Lewis, DP; Light, AR; Light, KC; Marshall-Gradisnik, S; McLaren-Howard, J; Mena, I; Miwa, K; Murovska, M; Stevens, SR (2012), Myalgic encephalomyelitis: Adult & Paediatric: International Consensus Primer for Medical Practitioners (PDF), ISBN 978-0-9739335-3-6
  25. ↑ Institute of Medicine (2015), Beyond Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Redefining an Illness, Washington, DC: The National Academies Press
  26. ↑ "'Symptom overlap is quite astounding': Researchers probe links between long-COVID and chronic fatigue". ABC News. March 17, 2022. Retrieved June 9, 2022.
  27. ↑ Sudre, Carole H.; Murray, Benjamin; Varsavsky, Thomas; Graham, Mark S.; Penfold, Rose S.; Bowyer, Ruth C.; Pujol, Joan Capdevila; Klaser, Kerstin; Antonelli, Michela (October 19, 2020). "Attributes and predictors of Long-COVID: analysis of COVID cases and their symptoms collected by the Covid Symptoms Study App". medRxiv: 2020.10.19.20214494. doi:10.1101/2020.10.19.20214494.
  28. ↑ Raveendran, A.V. (2021). "Long COVID-19: Challenges in the diagnosis and proposed diagnostic criteria". Diabetes & Metabolic Syndrome. 15 (1): 145–146. doi:10.1016/j.dsx.2020.12.025. ISSN 1871-4021. PMC 7737559. PMID 33341598.
  29. ↑ Komaroff, Anthony L.; Bateman, Lucinda (2021). "Will COVID-19 Lead to Myalgic Encephalomyelitis/Chronic Fatigue Syndrome?". Frontiers in Medicine. doi:10.3389/fmed.2020.606824. ISSN 2296-858X.
  30. ↑ Lambert, Natalie; Corps, Survivor; El-Azab, Sarah A.; Ramrakhiani, Nathan S.; Barisano, Anthony; Yu, Lu; Taylor, Kaitlyn; Esperanca, Alvaro; Downs, Charles A. (March 27, 2021). "COVID-19 Survivors' Reports of the Timing, Duration, and Health Impacts of Post-Acute Sequelae of SARS-CoV-2 (PASC) Infection". medRxiv: 2021.03.22.21254026. doi:10.1101/2021.03.22.21254026.
  31. ↑ Vanichkachorn, Greg; Newcomb, Richard; Cowl, Clayton T.; Murad, M. Hassan; Breeher, Laura; Miller, Sara; Trenary, Michael; Neveau, Daniel; Higgins, Steven (July 1, 2021). "Post–COVID-19 Syndrome (Long Haul Syndrome): Description of a Multidisciplinary Clinic at Mayo Clinic and Characteristics of the Initial Patient Cohort". Mayo Clinic Proceedings. 96 (7): 1782–1791. doi:10.1016/j.mayocp.2021.04.024. ISSN 0025-6196. PMID 34218857.
  32. ↑ Komaroff, Anthony L.; Lipkin, W. Ian (June 7, 2021). "Insights from myalgic encephalomyelitis/chronic fatigue syndrome may help unravel the pathogenesis of postacute COVID-19 syndrome". Trends in Molecular Medicine. doi:10.1016/j.molmed.2021.06.002. ISSN 1471-4914. PMID 34175230.
  33. ↑ Proal, Amy D.; VanElzakker, Michael B. (2021). "Long COVID or Post-acute Sequelae of COVID-19 (PASC): An Overview of Biological Factors That May Contribute to Persistent Symptoms". Frontiers in Microbiology. doi:10.3389/fmicb.2021.698169. ISSN 1664-302X. PMC 8260991. PMID 34248921.
  34. ↑ Greene, Chris; Connolly, Ruairi; Brennan, Declan; Laffan, Aoife; O’Keeffe, Eoin; Zaporojan, Lilia; O’Callaghan, Jeffrey; Thomson, Bennett; Connolly, Emma; Argue, Ruth; Martin-Loeches, Ignacio (February 22, 2024). "Blood–brain barrier disruption and sustained systemic inflammation in individuals with long COVID-associated cognitive impairment". Nature Neuroscience: 1–12. doi:10.1038/s41593-024-01576-9. ISSN 1546-1726.
  35. ↑ "A Detailed Study of Patients with Long-Haul COVID: An Analysis of Private Healthcare Claims. A FAIR Health White Paper" (PDF). FAIR Health. June 18, 2020.
  36. ↑ O'Dowd, Adrian (June 24, 2021). "Covid-19: Third of people infected have long term symptoms". BMJ. 373: n1626. doi:10.1136/bmj.n1626. ISSN 1756-1833. PMID 34168002.
  37. ↑ Torjesen, Ingrid (July 21, 2020). "NICE cautions against using graded exercise therapy for patients recovering from covid-19". The BMJ. 370. doi:10.1136/bmj.m2912. ISSN 1756-1833. PMID 32694164.

The BMJ (previously the British Medical Journal) is a weekly peer-reviewed medical journal.

BMJ The BMJ (previously the British Medical Journal) is a weekly peer-reviewed medical journal.

pacing The practice of staying within one's "energy envelope" or personal limit by combining periods of activity with periods of rest or avoiding exerting beyond a certain level. ME/CFS patients use pacing to avoid or reduce post-exertional malaise (PEM). Some patients use a heart rate monitor to help with pacing.

graded exercise therapy (GET) - A gradual increase in exercise or activity, according to a pre-defined plan. Focuses on overcoming the patient's alleged unhelpful illness beliefs that exertion can exacerbate symptoms, rather than on reversing physical deconditioning. Considered controversial, and possibly harmful, in the treatment or management of ME. One of the treatment arms of the controversial PACE trial.

See Graded exercise therapy.

graded exercise therapy (GET) - A gradual increase in exercise or activity, according to a pre-defined plan. Focuses on overcoming the patient's alleged unhelpful illness beliefs that exertion can exacerbate symptoms, rather than on reversing physical deconditioning. Considered controversial, and possibly harmful, in the treatment or management of ME. One of the treatment arms of the controversial PACE trial.

flare-up A symptoms flare in ME/CFS is a temporary increase in symptoms, alternatively known as experiencing post-exertional malaise. May be referred to as a "crash" or "collapse".

Centers for Disease Control and Prevention (CDC) - The Centers for Disease Control and Prevention is a U.S. government agency dedicated to epidemiology and public health. It operates under the auspices of the Department of Health and Human Services.

See Centers for Disease Control and Prevention.

National Institutes of Health (NIH) - A set of biomedical research institutes operated by the U.S. government, under the auspices of the Department of Health and Human Services.

BMJ The BMJ (previously the British Medical Journal) is a weekly peer-reviewed medical journal.

World Health Organization (WHO) - "A specialized agency of the United Nations that is concerned with public health. It was established on 7 April 1948, and is headquartered in Geneva, Switzerland. The WHO is a member of the United Nations Development Group. Its predecessor, the Health Organization, was an agency of the League of Nations." The International Statistical Classification of Diseases and Related Health Problems (ICD) is maintained by WHO.

See World Health Organization.

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