COVID-19

==Prognosis and risk factors==
<noinclude>{{See also|COVID-19 pandemic death rates by country}}</noinclude>
<!-- THE FOLLOWING TWO PARAGRAPHS ARE TRANSCLUDED INTO THE COVID-19 PANDEMIC ARTICLE -->

The severity of COVID‑19 varies. The disease may take a mild course with few or no symptoms, resembling other common upper respiratory diseases such as the [[common cold]]. In 3–4% of cases (7.4% for those over age 65) symptoms are severe enough to cause hospitalisation.<ref name="pmid33087398">{{#invoke:cite journal || vauthors = Doshi P | title = Will covid-19 vaccines save lives? Current trials aren't designed to tell us | journal = BMJ | volume = 371 | pages = m4037 | date = October 2020 | pmid = 33087398 | doi = 10.1136/bmj.m4037 | s2cid = 224817161 }}</ref> Mild cases typically recover within two weeks, while those with severe or critical diseases may take three to six weeks to recover. Among those who have died, the time from symptom onset to death has ranged from two to eight weeks.<ref name="WHOReport24Feb2020" /> The Italian [[Istituto Superiore di Sanità]] reported that the median time between the onset of symptoms and death was twelve days, with seven being hospitalised. However, people transferred to an ICU had a median time of ten days between hospitalisation and death.<ref name="ISSCharacteristics" /> Abnormal sodium levels during hospitalisation with COVID-19 are associated with poor prognoses: high sodium with a greater risk of death, and low sodium with an increased chance of needing ventilator support.<ref>{{#invoke:cite journal || vauthors = Tzoulis P, Waung JA, Bagkeris E, Hussein Z, Biddanda A, Cousins J, Dewsnip A, Falayi K, McCaughran W, Mullins C, Naeem A, Nwokolo M, Quah H, Bitat S, Deyab E, Ponnampalam S, Bouloux PM, Montgomery H, Baldeweg SE  | title = Dysnatremia is a Predictor for Morbidity and Mortality in Hospitalized Patients with COVID-19 | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 106 | issue = 6 | pages = 1637–1648 | date = May 2021 | pmid = 33624101 | pmc = 7928894 | doi = 10.1210/clinem/dgab107 }}</ref><ref>{{#invoke:cite journal || vauthors = Tzoulis P, Grossman AB, Baldeweg SE, Bouloux P, Kaltsas G | title = MANAGEMENT OF ENDOCRINE DISEASE: Dysnatraemia in COVID-19: prevalence, prognostic impact, pathophysiology, and management | journal = European Journal of Endocrinology | volume = 185 | issue = 4 | pages = R103–R111 | date = September 2021 | pmid = 34370712 | pmc = 8428074 | doi = 10.1530/EJE-21-0281 }}</ref> Prolonged [[prothrombin]] time and elevated [[C-reactive protein]] levels on admission to the hospital are associated with severe course of COVID‑19 and with a transfer to ICU.<ref>{{#invoke:cite journal || vauthors = Baranovskii DS, Klabukov ID, Krasilnikova OA, Nikogosov DA, Polekhina NV, Baranovskaia DR, Laberko LA, Maneksha S, Harry TV, Durbin RP  | title = Letter: Acid secretion by gastric mucous membrane | journal = The American Journal of Physiology | volume = 229 | issue = 6 | pages = 21–25 | date = December 1975 | pmid = 33210948<!-- Despite the error message it generates, the PMID is correct and valid as of 29 November 2020. --> | pmc = 7738209 | doi = 10.1080/03007995.2020.1853510 | s2cid = 227065216 }}</ref><ref>{{#invoke:cite journal || vauthors = Christensen B, Favaloro EJ, Lippi G, Van Cott EM | title = Hematology Laboratory Abnormalities in Patients with Coronavirus Disease 2019 (COVID-19) | journal = Seminars in Thrombosis and Hemostasis | volume = 46 | issue = 7 | pages = 845–849 | date = October 2020 | pmid = 32877961 | pmc = 7645834 | doi = 10.1055/s-0040-1715458 }}</ref>

Some early studies suggest 10% to 20% of people with COVID‑19 will experience [[Long COVID|symptoms lasting longer than a month]].<ref name="NIHRreportSep20">{{#invoke:cite journal||date=15 October 2020 |title=Living with Covid19 |url=https://evidence.nihr.ac.uk/themedreview/living-with-covid19/ |periodical=NIHR Themed Reviews |publisher=[[National Institute for Health Research]] |doi=10.3310/themedreview_41169 |doi-access=free |title-link=doi}}</ref><ref name="HvIJa">{{#invoke:Cite web||date=6 June 2020|title=How long does COVID-19 last?|url=https://covid.joinzoe.com/post/covid-long-term|access-date=15 October 2020|publisher=UK COVID Symptom Study}}</ref> A majority of those who were admitted to hospital with severe disease report long-term problems including fatigue and shortness of breath.<ref name="UniWashingtonSep20">{{#invoke:Cite web||url=https://www.doh.wa.gov/Portals/1/Documents/1600/coronavirus/SummaryCOVIDLong%20termHealthEffects9-1-2020.pdf |title=Summary of COVID-19 Long Term Health Effects: Emerging evidence and Ongoing Investigation |publisher=[[University of Washington]] |date=1 September 2020 |access-date=15 October 2020 |archive-date=18 December 2020 |archive-url=https://web.archive.org/web/20201218080009/https://www.doh.wa.gov/Portals/1/Documents/1600/coronavirus/SummaryCOVIDLong%20termHealthEffects9-1-2020.pdf |url-status=dead}}</ref> On 30 October 2020, WHO chief [[Tedros Adhanom]] warned that "to a significant number of people, the COVID virus poses a range of serious long-term effects". He has described the vast spectrum of COVID‑19 symptoms that fluctuate over time as "really concerning". They range from fatigue, a cough and shortness of breath, to inflammation and injury of major organs{{snd}}including the lungs and heart, and also neurological and psychologic effects. Symptoms often overlap and can affect any system in the body. Infected people have reported cyclical bouts of fatigue, headaches, months of complete exhaustion, mood swings, and other symptoms. Tedros therefore concluded that a strategy of achieving [[herd immunity]] by infection, rather than vaccination, is "morally unconscionable and unfeasible".<ref name="OaTsI">{{#invoke:Cite web|| title=Long-term symptoms of COVID-19 'really concerning', says WHO chief | website=UN News | date=30 October 2020 | url=https://news.un.org/en/story/2020/10/1076562 | access-date=7 March 2021}}</ref>

In terms of hospital readmissions about 9% of 106,000 individuals had to return for hospital treatment within two months of discharge. The average to readmit was eight days since first hospital visit. There are several risk factors that have been identified as being a cause of multiple admissions to a hospital facility. Among these are advanced age (above 65 years of age) and presence of a chronic condition such as diabetes, COPD, heart failure or chronic kidney disease.<ref name="rArHO">{{#invoke:Cite web||title=Coronavirus disease 2019 (COVID-19) – Prognosis |url=https://bestpractice.bmj.com/topics/en-us/3000168/prognosis |website=BMJ |access-date=15 November 2020}}</ref><ref name="CtbMg">{{#invoke:cite journal || vauthors = Lavery AM, Preston LE, Ko JY, Chevinsky JR, DeSisto CL, Pennington AF, Kompaniyets L, Datta SD, Click ES, Golden T, Goodman AB, Mac Kenzie WR, Boehmer TK, Gundlapalli AV  | title = Characteristics of Hospitalized COVID-19 Patients Discharged and Experiencing Same-Hospital Readmission – United States, March–August 2020 | journal = MMWR. Morbidity and Mortality Weekly Report | volume = 69 | issue = 45 | pages = 1695–1699 | date = November 2020 | pmid = 33180754 | pmc = 7660660 | doi = 10.15585/mmwr.mm6945e2 }}</ref>

According to [[scientific review]]s smokers are more likely to require intensive care or die compared to non-smokers.<ref>{{#invoke:cite journal || vauthors = Vardavas CI, Nikitara K | title = COVID-19 and smoking: A systematic review of the evidence | journal = Tobacco Induced Diseases | volume = 18 | pages = 20 | date = March 2020 | pmid = 32206052 | pmc = 7083240 | doi = 10.18332/tid/119324 }}</ref><ref name="engin-review">{{#invoke:cite journal || vauthors = Engin AB, Engin ED, Engin A | title = Two important controversial risk factors in SARS-CoV-2 infection: Obesity and smoking | journal = Environmental Toxicology and Pharmacology | volume = 78 | pages = 103411 | date = August 2020 | pmid = 32422280 | pmc = 7227557 | doi = 10.1016/j.etap.2020.103411 }}</ref> Acting on the same ACE2 pulmonary receptors affected by smoking, air pollution has been correlated with the disease.<ref name="engin-review" /> Short-term<ref>{{#invoke:cite journal || vauthors = Setti L, Passarini F, De Gennaro G, Barbieri P, Licen S, Perrone MG, Piazzalunga A, Borelli M, Palmisani J, Di Gilio A, Rizzo E, Colao A, Piscitelli P, Miani A  | title = Potential role of particulate matter in the spreading of COVID-19 in Northern Italy: first observational study based on initial epidemic diffusion | journal = BMJ Open | volume = 10 | issue = 9 | pages = e039338 | date = September 2020 | pmid = 32973066 | doi = 10.1136/bmjopen-2020-039338 | pmc = 7517216 }}</ref> and chronic<ref>{{#invoke:cite journal || vauthors = Wu X, Nethery RC, Sabath MB, Braun D, Dominici F | title = Air pollution and COVID-19 mortality in the United States: Strengths and limitations of an ecological regression analysis | journal = Science Advances | volume = 6 | issue = 45 | pages = eabd4049 | date = November 2020 | pmid = 33148655 | doi = 10.1126/sciadv.abd4049 | pmc = 7673673 | bibcode = 2020SciA....6.4049W }}</ref> exposure to air pollution seems to enhance morbidity and mortality from COVID‑19.<ref>{{#invoke:cite journal|| vauthors = Pansini R, Fornacca D |date=June 2021|title=Early Spread of COVID-19 in the Air-Polluted Regions of Eight Severely Affected Countries|journal=Atmosphere|volume=12|issue=6|pages=795|doi=10.3390/atmos12060795|bibcode=2021Atmos..12..795P|doi-access = free | title-link = doi }}</ref><ref>{{#invoke:cite journal || vauthors = Comunian S, Dongo D, Milani C, Palestini P | title = Air Pollution and Covid-19: The Role of Particulate Matter in the Spread and Increase of Covid-19's Morbidity and Mortality | journal = International Journal of Environmental Research and Public Health | volume = 17 | issue = 12 | pages = 4487 | date = June 2020 | pmid = 32580440 | doi = 10.3390/ijerph17124487 | pmc = 7345938 | doi-access = free | title-link = doi }}</ref><ref>{{#invoke:cite journal || vauthors = Domingo JL, Marquès M, Rovira J | title = Influence of airborne transmission of SARS-CoV-2 on COVID-19 pandemic. A review | journal = Environmental Research | volume = 188 | pages = 109861 | date = September 2020 | pmid = 32718835 | pmc = 7309850 | doi = 10.1016/j.envres.2020.109861 | bibcode = 2020ER....188j9861D }}</ref> Pre-existing heart and lung diseases<ref>{{#invoke:Cite web||url=https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-who-is-at-risk/art-20483301|title=COVID-19: Who's at higher risk of serious symptoms?|website=Mayo Clinic}}</ref> and also [[obesity]], especially in conjunction with [[fatty liver disease]], contributes to an increased health risk of COVID‑19.<ref name="engin-review" /><ref>{{#invoke:cite journal || vauthors = Tamara A, Tahapary DL | title = Obesity as a predictor for a poor prognosis of COVID-19: A systematic review | journal = Diabetes & Metabolic Syndrome | volume = 14 | issue = 4 | pages = 655–659 | date = July 2020 | pmid = 32438328 | pmc = 7217103 | doi = 10.1016/j.dsx.2020.05.020 | doi-access = free | title-link = doi }}</ref><ref>{{#invoke:cite journal || vauthors = Petrakis D, Margină D, Tsarouhas K, Tekos F, Stan M, Nikitovic D, Kouretas D, Spandidos DA, Tsatsakis A  | title = Obesity – A risk factor for increased COVID-19, severity and lethality (Review) | journal = Molecular Medicine Reports | volume = 22 | issue = 1 | pages = 9–19 | date = July 2020 | pmid = 32377709 | pmc = 7248467 | doi = 10.3892/mmr.2020.11127 | doi-access = free | title-link = doi }}</ref><ref>{{#invoke:cite journal ||vauthors=Roca-Fernández A, Dennis A, Nicholls R, McGonigle J, Kelly M, Banerjee R, Banerjee A, Sanyal AJ |date=29 March 2021 |title=Hepatic Steatosis, Rather Than Underlying Obesity, Increases the Risk of Infection and Hospitalization for COVID-19 |journal=Frontiers in Medicine |volume=8 |page=636637 |doi=10.3389/fmed.2021.636637 |pmid=33855033 |pmc=8039134 |issn=2296-858X|doi-access = free | title-link = doi }}</ref>

It is also assumed that those that are immunocompromised are at higher risk of getting severely sick from SARS-CoV-2.<ref>{{#invoke:Cite web||url=https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/immunocompromised.html|title=Coronavirus Disease 2019 (COVID-19)|date=11 February 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC) }}</ref> One research study that looked into the COVID‑19 infections in hospitalised kidney transplant recipients found a mortality rate of 11%.<ref>{{#invoke:cite journal || vauthors = Devresse A, Belkhir L, Vo B, Ghaye B, Scohy A, Kabamba B, Goffin E, De Greef J, Mourad M, De Meyer M, Yombi JC, Kanaan N  | title = COVID-19 Infection in Kidney Transplant Recipients: A Single-Center Case Series of 22 Cases From Belgium | journal = Kidney Medicine | volume = 2 | issue = 4 | pages = 459–466 | date = November 2020 | pmid = 32775986 | pmc = 7295531 | doi = 10.1016/j.xkme.2020.06.001 }}</ref>

Men with untreated [[hypogonadism]] were 2.4 times more likely than men with eugonadism to be hospitalised if they contracted COVID-19; Hypogonad men treated with [[testosterone]] were less likely to be hospitalised for COVID-19 than men who were not treated for hypogonadism.<ref name="jama">{{#invoke:cite journal || vauthors = Dhindsa S, Champion C, Deol E, Lui M, Campbell R, Newman J, Yeggalam A, Nadella S, Ahir V, Shrestha E, Kannampallil T, Diwan A  | title = Association of Male Hypogonadism With Risk of Hospitalization for COVID-19 | journal = JAMA Network Open | volume = 5 | issue = 9 | pages = e2229747 | date = September 2022 | pmid = 36053534 | doi = 10.1001/jamanetworkopen.2022.29747 | pmc = 9440397 }}</ref>

=== Genetic risk factors ===
[[Genetics]] plays an important role in the ability to fight off Covid.<ref name="pmid33888907">{{#invoke:cite journal || vauthors = Shelton JF, Shastri AJ, Ye C, Weldon CH, Filshtein-Sonmez T, Coker D, Symons A, Esparza-Gordillo J, Aslibekyan S, Auton A  | title = Trans-ancestry analysis reveals genetic and nongenetic associations with COVID-19 susceptibility and severity | journal = Nature Genetics | volume = 53 | issue = 6 | pages = 801–808 | date = June 2021 | pmid = 33888907 | doi = 10.1038/s41588-021-00854-7 | s2cid = 233372385 }}</ref> For instance, those that do not produce detectable [[type I interferon]]s or produce [[Autoantibody|auto-antibodies]] against these may get much sicker from COVID‑19.<ref>{{#invoke:Cite web||title=One in Seven Dire COVID Cases May Result from a Faulty Immune Response|url=https://www.scientificamerican.com/article/one-in-seven-dire-covid-cases-may-result-from-a-faulty-immune-response/|website=Scientific American|vauthors=Wallis C}}</ref><ref>{{#invoke:cite journal || vauthors = Bastard P, Rosen LB, Zhang Q, Michailidis E, Hoffmann HH, Zhang Y, Dorgham K, Philippot Q, Rosain J, Béziat V, Manry J, Shaw E, Haljasmägi L, Peterson P, Lorenzo L, Bizien L, Trouillet-Assant S, Dobbs K, de Jesus AA, Belot A, Kallaste A, Catherinot E, Tandjaoui-Lambiotte Y, Le Pen J, Kerner G, Bigio B, Seeleuthner Y, Yang R, Bolze A, Spaan AN, Delmonte OM, Abers MS, Aiuti A, Casari G, Lampasona V, Piemonti L, Ciceri F, Bilguvar K, Lifton RP, Vasse M, Smadja DM, Migaud M, Hadjadj J, Terrier B, Duffy D, Quintana-Murci L, van de Beek D, Roussel L, Vinh DC, Tangye SG, Haerynck F, Dalmau D, Martinez-Picado J, Brodin P, Nussenzweig MC, Boisson-Dupuis S, Rodríguez-Gallego C, Vogt G, Mogensen TH, Oler AJ, Gu J, Burbelo PD, Cohen JI, Biondi A, Bettini LR, D'Angio M, Bonfanti P, Rossignol P, Mayaux J, Rieux-Laucat F, Husebye ES, Fusco F, Ursini MV, Imberti L, Sottini A, Paghera S, Quiros-Roldan E, Rossi C, Castagnoli R, Montagna D, Licari A, Marseglia GL, Duval X, Ghosn J, Tsang JS, Goldbach-Mansky R, Kisand K, Lionakis MS, Puel A, Zhang SY, Holland SM, Gorochov G, Jouanguy E, Rice CM, Cobat A, Notarangelo LD, Abel L, Su HC, Casanova JL  | title = Autoantibodies against type I IFNs in patients with life-threatening COVID-19 | journal = Science | volume = 370 | issue = 6515 | pages = eabd4585 | date = October 2020 | pmid = 32972996 | pmc = 7857397 | doi = 10.1126/science.abd4585 | s2cid = 221914095 | title-link = doi | doi-access = free }}</ref> [[Genetic screening]] is able to detect interferon effector genes.<ref>{{#invoke:cite journal || vauthors = Fusco DN, Brisac C, John SP, Huang YW, Chin CR, Xie T, Zhao H, Jilg N, Zhang L, Chevaliez S, Wambua D, Lin W, Peng L, Chung RT, Brass AL  | title = A genetic screen identifies interferon-α effector genes required to suppress hepatitis C virus replication | journal = Gastroenterology | volume = 144 | issue = 7 | pages = 1438–49, 1449.e1-9 | date = June 2013 | pmid = 23462180 | pmc = 3665646 | doi = 10.1053/j.gastro.2013.02.026 }}</ref> Some genetic variants are risk factors in specific populations. For instance, an [[allele]] of the [[DOCK2]] gene (dedicator of cytokinesis 2 gene) is a common risk factor in Asian populations but much less common in Europe. The mutation leads to lower expression of DOCK2 especially in younger patients with severe Covid.<ref>{{#invoke:cite journal || vauthors = Namkoong H, Edahiro R, Takano T, Nishihara H, Shirai Y, Sonehara K, Tanaka H, Azekawa S, Mikami Y, Lee H, Hasegawa T, Okudela K, Okuzaki D, Motooka D, Kanai M, Naito T, Yamamoto K, Wang QS, Saiki R, Ishihara R, Matsubara Y, Hamamoto J, Hayashi H, Yoshimura Y, Tachikawa N, Yanagita E, Hyugaji T, Shimizu E, Katayama K, Kato Y, Morita T, Takahashi K, Harada N, Naito T, Hiki M, Matsushita Y, Takagi H, Aoki R, Nakamura A, Harada S, Sasano H, Kabata H, Masaki K, Kamata H, Ikemura S, Chubachi S, Okamori S, Terai H, Morita A, Asakura T, Sasaki J, Morisaki H, Uwamino Y, Nanki K, Uchida S, Uno S, Nishimura T, Ishiguro T, Isono T, Shibata S, Matsui Y, Hosoda C, Takano K, Nishida T, Kobayashi Y, Takaku Y, Takayanagi N, Ueda S, Tada A, Miyawaki M, Yamamoto M, Yoshida E, Hayashi R, Nagasaka T, Arai S, Kaneko Y, Sasaki K, Tagaya E, Kawana M, Arimura K, Takahashi K, Anzai T, Ito S, Endo A, Uchimura Y, Miyazaki Y, Honda T, Tateishi T, Tohda S, Ichimura N, Sonobe K, Sassa CT, Nakajima J, Nakano Y, Nakajima Y, Anan R, Arai R, Kurihara Y, Harada Y, Nishio K, Ueda T, Azuma M, Saito R, Sado T, Miyazaki Y, Sato R, Haruta Y, Nagasaki T, Yasui Y, Hasegawa Y, Mutoh Y, Kimura T, Sato T, Takei R, Hagimoto S, Noguchi Y, Yamano Y, Sasano H, Ota S, Nakamori Y, Yoshiya K, Saito F, Yoshihara T, Wada D, Iwamura H, Kanayama S, Maruyama S, Yoshiyama T, Ohta K, Kokuto H, Ogata H, Tanaka Y, Arakawa K, Shimoda M, Osawa T, Tateno H, Hase I, Yoshida S, Suzuki S, Kawada M, Horinouchi H, Saito F, Mitamura K, Hagihara M, Ochi J, Uchida T, Baba R, Arai D, Ogura T, Takahashi H, Hagiwara S, Nagao G, Konishi S, Nakachi I, Murakami K, Yamada M, Sugiura H, Sano H, Matsumoto S, Kimura N, Ono Y, Baba H, Suzuki Y, Nakayama S, Masuzawa K, Namba S, Suzuki K, Naito Y, Liu YC, Takuwa A, Sugihara F, Wing JB, Sakakibara S, Hizawa N, Shiroyama T, Miyawaki S, Kawamura Y, Nakayama A, Matsuo H, Maeda Y, Nii T, Noda Y, Niitsu T, Adachi Y, Enomoto T, Amiya S, Hara R, Yamaguchi Y, Murakami T, Kuge T, Matsumoto K, Yamamoto Y, Yamamoto M, Yoneda M, Kishikawa T, Yamada S, Kawabata S, Kijima N, Takagaki M, Sasa N, Ueno Y, Suzuki M, Takemoto N, Eguchi H, Fukusumi T, Imai T, Fukushima M, Kishima H, Inohara H, Tomono K, Kato K, Takahashi M, Matsuda F, Hirata H, Takeda Y, Koh H, Manabe T, Funatsu Y, Ito F, Fukui T, Shinozuka K, Kohashi S, Miyazaki M, Shoko T, Kojima M, Adachi T, Ishikawa M, Takahashi K, Inoue T, Hirano T, Kobayashi K, Takaoka H, Watanabe K, Miyazawa N, Kimura Y, Sado R, Sugimoto H, Kamiya A, Kuwahara N, Fujiwara A, Matsunaga T, Sato Y, Okada T, Hirai Y, Kawashima H, Narita A, Niwa K, Sekikawa Y, Nishi K, Nishitsuji M, Tani M, Suzuki J, Nakatsumi H, Ogura T, Kitamura H, Hagiwara E, Murohashi K, Okabayashi H, Mochimaru T, Nukaga S, Satomi R, Oyamada Y, Mori N, Baba T, Fukui Y, Odate M, Mashimo S, Makino Y, Yagi K, Hashiguchi M, Kagyo J, Shiomi T, Fuke S, Saito H, Tsuchida T, Fujitani S, Takita M, Morikawa D, Yoshida T, Izumo T, Inomata M, Kuse N, Awano N, Tone M, Ito A, Nakamura Y, Hoshino K, Maruyama J, Ishikura H, Takata T, Odani T, Amishima M, Hattori T, Shichinohe Y, Kagaya T, Kita T, Ohta K, Sakagami S, Koshida K, Hayashi K, Shimizu T, Kozu Y, Hiranuma H, Gon Y, Izumi N, Nagata K, Ueda K, Taki R, Hanada S, Kawamura K, Ichikado K, Nishiyama K, Muranaka H, Nakamura K, Hashimoto N, Wakahara K, Sakamoto K, Omote N, Ando A, Kodama N, Kaneyama Y, Maeda S, Kuraki T, Matsumoto T, Yokote K, Nakada TA, Abe R, Oshima T, Shimada T, Harada M, Takahashi T, Ono H, Sakurai T, Shibusawa T, Kimizuka Y, Kawana A, Sano T, Watanabe C, Suematsu R, Sageshima H, Yoshifuji A, Ito K, Takahashi S, Ishioka K, Nakamura M, Masuda M, Wakabayashi A, Watanabe H, Ueda S, Nishikawa M, Chihara Y, Takeuchi M, Onoi K, Shinozuka J, Sueyoshi A, Nagasaki Y, Okamoto M, Ishihara S, Shimo M, Tokunaga Y, Kusaka Y, Ohba T, Isogai S, Ogawa A, Inoue T, Fukuyama S, Eriguchi Y, Yonekawa A, Kan-O K, Matsumoto K, Kanaoka K, Ihara S, Komuta K, Inoue Y, Chiba S, Yamagata K, Hiramatsu Y, Kai H, Asano K, Oguma T, Ito Y, Hashimoto S, Yamasaki M, Kasamatsu Y, Komase Y, Hida N, Tsuburai T, Oyama B, Takada M, Kanda H, Kitagawa Y, Fukuta T, Miyake T, Yoshida S, Ogura S, Abe S, Kono Y, Togashi Y, Takoi H, Kikuchi R, Ogawa S, Ogata T, Ishihara S, Kanehiro A, Ozaki S, Fuchimoto Y, Wada S, Fujimoto N, Nishiyama K, Terashima M, Beppu S, Yoshida K, Narumoto O, Nagai H, Ooshima N, Motegi M, Umeda A, Miyagawa K, Shimada H, Endo M, Ohira Y, Watanabe M, Inoue S, Igarashi A, Sato M, Sagara H, Tanaka A, Ohta S, Kimura T, Shibata Y, Tanino Y, Nikaido T, Minemura H, Sato Y, Yamada Y, Hashino T, Shinoki M, Iwagoe H, Takahashi H, Fujii K, Kishi H, Kanai M, Imamura T, Yamashita T, Yatomi M, Maeno T, Hayashi S, Takahashi M, Kuramochi M, Kamimaki I, Tominaga Y, Ishii T, Utsugi M, Ono A, Tanaka T, Kashiwada T, Fujita K, Saito Y, Seike M, Watanabe H, Matsuse H, Kodaka N, Nakano C, Oshio T, Hirouchi T, Makino S, Egi M, Omae Y, Nannya Y, Ueno T, Katayama K, Ai M, Fukui Y, Kumanogoh A, Sato T, Hasegawa N, Tokunaga K, Ishii M, Koike R, Kitagawa Y, Kimura A, Imoto S, Miyano S, Ogawa S, Kanai T, Fukunaga K, Okada Y  | title = DOCK2 is involved in the host genetics and biology of severe COVID-19 | journal = Nature | volume = 609 | issue = 7928 | pages = 754–760 | date = September 2022 | pmid = 35940203 | pmc = 9492544 | doi = 10.1038/s41586-022-05163-5 | bibcode = 2022Natur.609..754N }}</ref> In fact, many other genes and genetic variants have been found that determine the outcome of SARS-CoV-2 infections.<ref>{{#invoke:cite journal || vauthors = Kousathanas A, Pairo-Castineira E, Rawlik K, Stuckey A, Odhams CA, Walker S, Russell CD, Malinauskas T, Wu Y, Millar J, Shen X, Elliott KS, Griffiths F, Oosthuyzen W, Morrice K, Keating S, Wang B, Rhodes D, Klaric L, Zechner M, Parkinson N, Siddiq A, Goddard P, Donovan S, Maslove D, Nichol A, Semple MG, Zainy T, Maleady-Crowe F, Todd L, Salehi S, Knight J, Elgar G, Chan G, Arumugam P, Patch C, Rendon A, Bentley D, Kingsley C, Kosmicki JA, Horowitz JE, Baras A, Abecasis GR, Ferreira MA, Justice A, Mirshahi T, Oetjens M, Rader DJ, Ritchie MD, Verma A, Fowler TA, Shankar-Hari M, Summers C, Hinds C, Horby P, Ling L, McAuley D, Montgomery H, Openshaw PJ, Elliott P, Walsh T, Tenesa A, Fawkes A, Murphy L, Rowan K, Ponting CP, Vitart V, Wilson JF, Yang J, Bretherick AD, Scott RH, Hendry SC, Moutsianas L, Law A, Caulfield MJ, Baillie JK  | title = Whole-genome sequencing reveals host factors underlying critical COVID-19 | journal = Nature | volume = 607 | issue = 7917 | pages = 97–103 | date = July 2022 | pmid = 35255492 | pmc = 9259496 | doi = 10.1038/s41586-022-04576-6 }}</ref>

=== Children ===
{{See also|Impact of the COVID-19 pandemic on children}}

While very young children have experienced lower rates of infection, older children have a rate of infection that is similar to the population as a whole.<ref>{{#invoke:Cite web||title=COVID-19 in children and the role of school settings in transmission – first update |url=https://www.ecdc.europa.eu/en/publications-data/children-and-school-settings-covid-19-transmission |website=European Centre for Disease Prevention and Control |access-date=6 April 2021 |date=23 December 2020}}</ref><ref>{{#invoke:Cite web||title=Estimated Disease Burden of COVID-19 |url=https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burden.html |website=U.S. [[Centers for Disease Control and Prevention]] (CDC) |access-date=6 April 2021 |date=11 February 2020}}</ref> Children are likely to have milder symptoms and are at lower risk of severe disease than adults.<ref name="Reardon">{{#invoke:cite journal || vauthors = Reardon S |title=Why don't kids tend to get as sick from Covid-19? |journal=[[Knowable Magazine]] |date=2 September 2021 |doi=10.1146/knowable-090121-1 |s2cid=239653475 |url=https://knowablemagazine.org/article/health-disease/2021/why-dont-kids-tend-get-sick-covid19 |access-date=7 September 2021}}</ref> The CDC reports that in the US roughly a third of hospitalised children were admitted to the ICU,<ref>{{#invoke:Cite web||title=Information for Pediatric Healthcare Providers |url=https://www.cdc.gov/coronavirus/2019-ncov/hcp/pediatric-hcp.html |website=U.S. [[Centers for Disease Control and Prevention]] (CDC) |access-date=6 April 2021 |date=11 February 2020}}</ref> while a European multinational study of hospitalised children from June 2020, found that about 8% of children admitted to a hospital needed intensive care.<ref>{{#invoke:cite journal || vauthors = Götzinger F, Santiago-García B, Noguera-Julián A, Lanaspa M, Lancella L, Calò Carducci FI, Gabrovska N, Velizarova S, Prunk P, Osterman V, Krivec U, Lo Vecchio A, Shingadia D, Soriano-Arandes A, Melendo S, Lanari M, Pierantoni L, Wagner N, L'Huillier AG, Heininger U, Ritz N, Bandi S, Krajcar N, Roglić S, Santos M, Christiaens C, Creuven M, Buonsenso D, Welch SB, Bogyi M, Brinkmann F, Tebruegge M  | title = COVID-19 in children and adolescents in Europe: a multinational, multicentre cohort study | journal = The Lancet. Child & Adolescent Health | volume = 4 | issue = 9 | pages = 653–661 | date = September 2020 | pmid = 32593339 | pmc = 7316447 | doi = 10.1016/S2352-4642(20)30177-2 }}</ref> Four of the 582 children (0.7%) in the European study died, but the actual mortality rate may be "substantially lower" since milder cases that did not seek medical help were not included in the study.<ref>{{#invoke:cite journal || vauthors = Fang L, Karakiulakis G, Roth M | title = Are patients with hypertension and diabetes mellitus at increased risk for COVID-19 infection? | journal = The Lancet. Respiratory Medicine | volume = 8 | issue = 4 | pages = e21 | date = April 2020 | pmid = 32171062 | pmc = 7118626 | doi = 10.1016/S0140-6736(20)30311-1 }}</ref><ref name="CDC 2020children">{{#invoke:Cite web||url=https://www.cdc.gov/coronavirus/2019-ncov/specific-groups/children-faq.html|title=Coronavirus Disease 2019 (COVID-19)|date=11 February 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC) |access-date=2 March 2020|archive-url=https://web.archive.org/web/20200302064104/https://www.cdc.gov/coronavirus/2019-ncov/specific-groups/children-faq.html|archive-date=2 March 2020|url-status=live}}</ref>

=== Long-term effects ===
{{Further|Long COVID}}

Around 10% to 30% of non-hospitalised people with COVID-19 go on to develop [[long COVID]]. For those that do need hospitalisation, the incidence of long-term effects is over 50%.<ref name="davis">{{#invoke:cite journal ||vauthors=Davis HE, McCorkell L, Vogel JM, Topol EJ |date=March 2023 |title=Long COVID: major findings, mechanisms and recommendations |journal=Nature Reviews. Microbiology |volume=21 |issue=3 |pages=133–146 |doi=10.1038/s41579-022-00846-2 |pmc=9839201 |pmid=36639608}}</ref> Long COVID is an often severe multisystem disease with a large set of symptoms. There are likely various, possibly coinciding, causes.<ref name="davis" /> Organ damage from the acute infection can explain a part of the symptoms, but long COVID is also observed in people where organ damage seems to be absent.<ref name="pmid35594336">{{#invoke:cite journal ||vauthors=Castanares-Zapatero D, Chalon P, Kohn L, Dauvrin M, Detollenaere J, Maertens de Noordhout C, Primus-de Jong C, Cleemput I, Van den Heede K |date=December 2022 |title=Pathophysiology and mechanism of long COVID: a comprehensive review |url= |journal=Annals of Medicine |volume=54 |issue=1 |pages=1473–1487 |doi=10.1080/07853890.2022.2076901 |pmc=9132392 |pmid=35594336}}</ref>

By a variety of mechanisms, the lungs are the organs most affected in COVID{{nbhyph}}19.<ref name="Torres">{{#invoke:cite journal || vauthors = Torres-Castro R, Vasconcello-Castillo L, Alsina-Restoy X, Solis-Navarro L, Burgos F, Puppo H, Vilaró J  | title = Respiratory function in patients post-infection by COVID-19: a systematic review and meta-analysis | journal = Pulmonology | date = November 2020 | volume = 27 | issue = 4 | pages = 328–337 | pmid = 33262076 | pmc = 7687368 | doi = 10.1016/j.pulmoe.2020.10.013 | publisher = Elsevier BV | s2cid = 227162748 }}</ref> In people requiring hospital admission, up to 98% of CT scans performed show lung abnormalities after 28 days of illness even if they had clinically improved.<ref>{{#invoke:cite journal || vauthors = Shaw B, Daskareh M, Gholamrezanezhad A | title = The lingering manifestations of COVID-19 during and after convalescence: update on long-term pulmonary consequences of coronavirus disease 2019 (COVID-19) | journal = La Radiologia Medica | volume = 126 | issue = 1 | pages = 40–46 | date = January 2021 | pmid = 33006087 | pmc = 7529085 | doi = 10.1007/s11547-020-01295-8 }}</ref> People with advanced age, severe disease, prolonged ICU stays, or who smoke are more likely to have long-lasting effects, including pulmonary fibrosis.<ref name="Rai">{{#invoke:cite journal || vauthors = Zhao YM, Shang YM, Song WB, Li QQ, Xie H, Xu QF, Jia JL, Li LM, Mao HL, Zhou XM, Luo H, Gao YF, Xu AG  | title = Follow-up study of the pulmonary function and related physiological characteristics of COVID-19 survivors three months after recovery | journal = eClinicalMedicine | volume = 25 | pages = 100463 | date = August 2020 | pmc = 7654356 | doi = 10.1016/j.ijtb.2020.11.003 | pmid = 32838236 }}</ref> Overall, approximately one-third of those investigated after four weeks will have findings of [[pulmonary fibrosis]] or reduced lung function as measured by [[DLCO]], even in asymptomatic people, but with the suggestion of continuing improvement with the passing of more time.<ref name="Torres" /> After severe disease, lung function can take anywhere from three months to a year or more to return to previous levels.<ref>{{#invoke:Cite news||title=COVID-19 Lung Damage |url=https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/what-coronavirus-does-to-the-lungs |publisher=Johns Hopkins Medicine |access-date=21 May 2022 |date=28 February 2022}}</ref>

The risks of [[cognitive deficit]], [[dementia]], psychotic disorders, and [[epilepsy]] or seizures persists at an increased level two years after infection.<ref>{{#invoke:cite journal ||vauthors=Taquet M, Sillett R, Zhu L, Mendel J, Camplisson I, Dercon Q, Harrison PJ  |date=August 2022 |title=Neurological and psychiatric risk trajectories after SARS-CoV-2 infection: an analysis of 2-year retrospective cohort studies including 1 284 437 patients |journal=The Lancet Psychiatry |doi=10.1016/S2215-0366(22)00260-7 |pmid=35987197 |pmc=9385200 |s2cid=251626731 |issn=2215-0366 |volume=9 |issue=10 |pages=815–827}}</ref>

=== Immunity ===
{{See also|COVID-19 vaccine}}
[[File:Diagnostics-10-00453-g001.webp|thumb|Human [[antibody response]] to SARS-CoV-2 infection]]

The [[immune response]] by humans to SARS-CoV-2 virus occurs as a combination of the [[cell-mediated immunity]] and antibody production,<ref>{{#invoke:Cite web||url=https://www.ecdc.europa.eu/en/covid-19/latest-evidence/immune-responses |title=Immune responses and correlates of protective immunity against SARS-CoV-2 |date=18 May 2021 |publisher=European Centre for Disease Prevention and Control |access-date=3 June 2021}}</ref> just as with most other infections.<ref>{{#invoke:cite journal || vauthors = Vabret N, Britton GJ, Gruber C, Hegde S, Kim J, Kuksin M, Levantovsky R, Malle L, Moreira A, Park MD, Pia L, Risson E, Saffern M, Salomé B, Esai Selvan M, Spindler MP, Tan J, van der Heide V, Gregory JK, Alexandropoulos K, Bhardwaj N, Brown BD, Greenbaum B, Gümüş ZH, Homann D, Horowitz A, Kamphorst AO, Curotto de Lafaille MA, Mehandru S, Merad M, Samstein RM  | title = Immunology of COVID-19: Current State of the Science | journal = Immunity | volume = 52 | issue = 6 | pages = 910–941 | date = June 2020 | pmid = 32505227 | pmc = 7200337 | doi = 10.1016/j.immuni.2020.05.002 | doi-access = free | title-link = doi }}</ref> B cells interact with T cells and begin dividing before selection into the plasma cell, partly on the basis of their affinity for antigen.<ref>{{#invoke:cite journal || vauthors = Wang Z, Muecksch F, Schaefer-Babajew D, Finkin S, Viant C, Gaebler C, Hoffmann HH, Barnes CO, Cipolla M, Ramos V, Oliveira TY, Cho A, Schmidt F, Da Silva J, Bednarski E, Aguado L, Yee J, Daga M, Turroja M, Millard KG, Jankovic M, Gazumyan A, Zhao Z, Rice CM, Bieniasz PD, Caskey M, Hatziioannou T, Nussenzweig MC  | title = Naturally enhanced neutralizing breadth against SARS-CoV-2 one year after infection | journal = Nature | volume = 595 | issue = 7867 | pages = 426–431 | date = July 2021 | pmid = 34126625 | pmc = 8277577 | doi = 10.1038/s41586-021-03696-9 | bibcode = 2021Natur.595..426W }}</ref> Since SARS-CoV-2 has been in the human population only since December 2019, it remains unknown if the [[Immunity (medical)|immunity]] is long-lasting in people who recover from the disease.<ref name="CohenJI2020Dec">{{#invoke:cite journal || vauthors = Cohen JI, Burbelo PD | title = Reinfection with SARS-CoV-2: Implications for Vaccines | journal = Clinical Infectious Diseases | date = December 2020 | pmid = 33338197 | pmc = 7799323 | doi = 10.1093/cid/ciaa1866 | s2cid = 229323810 | title-link = doi | volume = 73 | issue = 11 | pages = e4223–e4228 | doi-access = free }}</ref> The presence of neutralising antibodies in blood strongly correlates with protection from infection, but the level of neutralising antibody declines with time. Those with asymptomatic or mild disease had undetectable levels of neutralising antibody two months after infection. In another study, the level of neutralising antibodies fell four-fold one to four months after the onset of symptoms. However, the lack of antibodies in the blood does not mean antibodies will not be rapidly produced upon reexposure to SARS-CoV-2. Memory B cells specific for the spike and nucleocapsid proteins of SARS-CoV-2 last for at least six months after the appearance of symptoms.<ref name="CohenJI2020Dec" />

As of August 2021, reinfection with COVID‑19 was possible but uncommon. The first case of reinfection was documented in August 2020.<ref name="Wang-2021">{{#invoke:cite journal || vauthors = Wang J, Kaperak C, Sato T, Sakuraba A | title = COVID-19 reinfection: a rapid systematic review of case reports and case series | journal = Journal of Investigative Medicine | volume = 69 | issue = 6 | pages = 1253–1255 | date = August 2021 | pmid = 34006572 | doi = 10.1136/jim-2021-001853 |issn=1081-5589 | s2cid = 234773697 }}</ref> A systematic review found 17 cases of confirmed reinfection in medical literature as of May 2021.<ref name="Wang-2021" /> With the [[SARS-CoV-2 Omicron variant|Omicron variant]], as of 2022, reinfections have become common, albeit it is unclear how common.<ref name="abc-reinfections"/> [[SARS-CoV-2#Reinfection|COVID-19 reinfections]] are thought to likely be less severe than primary infections, especially if one was previously infected by the same variant.<ref name="abc-reinfections">{{#invoke:cite news ||title=How soon after catching COVID-19 can you get it again? |url=https://www.abc.net.au/news/health/2022-05-03/covid-19-reinfection-what-are-the-odds-of-catching-it-twice/101024180 |access-date=24 June 2022 |work=ABC News |date=2 May 2022 }}</ref>{{additional citation needed|date=July 2022}}