COVID-19

=== Comorbidities ===
[[biology|Biological]] factors (immune response) and the general behaviour (habits) can strongly determine the consequences of COVID‑19.<ref name="Dehingia-2021" /> Most of those who die of COVID‑19 have [[pre-existing condition|pre-existing (underlying) conditions]], including hypertension, [[diabetes mellitus]],<ref name="Shauly-Aharonov-2021" /> and [[cardiovascular disease]].<ref name="WHO-2020a">{{#invoke:Cite web||url=https://www.who.int/dg/speeches/detail/who-director-general-s-statement-on-the-advice-of-the-ihr-emergency-committee-on-novel-coronavirus |title=WHO Director-General's statement on the advice of the IHR Emergency Committee on Novel Coronavirus |website=[[World Health Organization]] (WHO)}}</ref> According to March data from the United States, 89% of those hospitalised had preexisting conditions.<ref>{{#invoke:cite journal || vauthors = Garg S, Kim L, Whitaker M, O'Halloran A, Cummings C, Holstein R, Prill M, Chai SJ, Kirley PD, Alden NB, Kawasaki B, Yousey-Hindes K, Niccolai L, Anderson EJ, Openo KP, Weigel A, Monroe ML, Ryan P, Henderson J, Kim S, Como-Sabetti K, Lynfield R, Sosin D, Torres S, Muse A, Bennett NM, Billing L, Sutton M, West N, Schaffner W, Talbot HK, Aquino C, George A, Budd A, Brammer L, Langley G, Hall AJ, Fry A  | title = Hospitalization Rates and Characteristics of Patients Hospitalized with Laboratory-Confirmed Coronavirus Disease 2019 – COVID-NET, 14 States, March 1–30, 2020 | journal = MMWR. Morbidity and Mortality Weekly Report | volume = 69 | issue = 15 | pages = 458–464 | date = April 2020 | pmid = 32298251 | pmc = 7755063 | doi = 10.15585/mmwr.mm6915e3 | title-link = doi | doi-access = free }}</ref> The Italian Istituto Superiore di Sanità reported that out of 8.8% of deaths where [[medical record|medical charts]] were available, 96.1% of people had at least one [[comorbidity]] with the average person having 3.4 diseases.<ref name="ISSCharacteristics">{{#invoke:cite report||url=https://www.epicentro.iss.it/en/coronavirus/bollettino/Report-COVID-2019_22_July_2020.pdf|title=Characteristics of SARS-CoV-2 patients dying in Italy Report based on available data on July 22nd, 2020|date=22 July 2020|publisher=[[Istituto Superiore di Sanità]]|access-date=4 October 2020|vauthors=Palmieri L, Andrianou X, Barbariol P, Bella A, Bellino S, Benelli E, Bertinato L, Boros S, Brambilla G, Calcagnini G, Canevelli M, Castrucci MR, Censi F, Ciervo A, Colaizzo E, D'Ancona F, Del Manso M, Donfrancesco C, Fabiani M, Filia A, Floridia M, Giuliano M, Grisetti T, Langer M, Lega I, Lo Noce C, Maiozzi P, Malchiodi Albedi F, Manno V, Martini M, Mateo Urdiales A, Mattei E, Meduri C, Meli P, Minelli G, Nebuloni M, Nisticò L, Nonis M, Onder G, Palmisano L, Petrosillo N, Pezzotti P, Pricci F, Punzo O, Puro V, Raparelli V, Rezza G, Riccardo F, Rota MC, Salerno P, Serra D, Siddu A, Stefanelli P, Tamburo De Bella M, Tiple D, Unim B, Vaianella L, Vanacore N, Vichi M, Villani ER, Brusaferro S}}</ref> According to this report the most common comorbidities are hypertension (66% of deaths), [[type&nbsp;2 diabetes]] (29.8% of deaths), [[ischemic heart disease|ischaemic heart disease]] (27.6% of deaths), [[atrial fibrillation]] (23.1% of deaths) and [[chronic renal failure]] (20.2% of deaths).

Most critical respiratory comorbidities according to the US [[Centers for Disease Control and Prevention]] (CDC), are: moderate or severe [[asthma]], pre-existing [[Chronic obstructive pulmonary disease|COPD]], [[pulmonary fibrosis]], [[cystic fibrosis]].<ref>{{#invoke:Cite web||date=11 February 2020|title=Coronavirus Disease 2019 (COVID-19)|url=https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/groups-at-higher-risk.html|access-date=19 June 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC) }}</ref> Evidence stemming from [[meta-analysis]] of several smaller research papers also suggests that smoking can be associated with worse outcomes.<ref>{{#invoke:cite journal || vauthors = Zhao Q, Meng M, Kumar R, Wu Y, Huang J, Lian N, Deng Y, Lin S  | title = The impact of COPD and smoking history on the severity of COVID-19: A systemic review and meta-analysis | journal = Journal of Medical Virology | volume = 92 | issue = 10 | pages = 1915–1921 | date = October 2020 | pmid = 32293753 | pmc = 7262275 | doi = 10.1002/jmv.25889 }}</ref><ref>{{#invoke:Cite web||title=Smoking and COVID-19|url=https://www.who.int/news-room/commentaries/detail/smoking-and-covid-19|access-date=19 June 2020|website=[[World Health Organization]] (WHO)}}</ref> When someone with existing respiratory problems is infected with COVID‑19, they might be at greater risk for severe symptoms.<ref>{{#invoke:Cite web||title=Coronavirus Disease 2019 (COVID-19)|url=https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/groups-at-higher-risk.html|date=11 February 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC) |access-date=4 May 2020}}</ref> COVID‑19 also poses a greater risk to people who [[Opioid use disorder|misuse opioids]] and [[Stimulant use disorder|amphetamines]], insofar as their drug use may have caused lung damage.<ref>{{#invoke:Cite web||title=People who use drugs are more vulnerable to coronavirus. Here's what clinics are doing to help.|url=https://www.theadvocate.com/baton_rouge/news/coronavirus/article_f80cf77e-84fa-11ea-88d5-2b37dc9dd966.html| vauthors = DeRobertis J |date=3 May 2020|website=The Advocate (Louisiana)|access-date=4 May 2020}}</ref>

In August 2020, the CDC issued a caution that [[tuberculosis]] (TB) infections could increase the risk of severe illness or death. The WHO recommended that people with respiratory symptoms be screened for both diseases, as testing positive for COVID‑19 could not rule out co-infections. Some projections have estimated that reduced TB detection due to the pandemic could result in 6.3&nbsp;million additional TB cases and 1.4&nbsp;million TB-related deaths by 2025.<ref>{{#invoke:Cite web||url=https://www.cdc.gov/coronavirus/2019-ncov/global-covid-19/TB-non-us-settings.html|title=Coronavirus Disease 2019 (COVID-19)|date=11 February 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC) }}</ref>