Editing Infection (section)

== Susceptibility to infection ==
Pandemics such as [[COVID-19]] show that people dramatically differ in their susceptibility to infection. This may be because of general health, age, or their immune status, e.g. when they have been infected previously. However, it also has become clear that there are genetic factor which determine susceptibility to infection. For instance, up to 40% of [[SARS-CoV-2]] infections may be asymptomatic, suggesting that many people are naturally protected from disease.<ref>{{Cite journal |last1=Oran |first1=Daniel P. |last2=Topol |first2=Eric J. |date=2020-09-01 |title=Prevalence of Asymptomatic SARS-CoV-2 Infection : A Narrative Review |journal=Annals of Internal Medicine |volume=173 |issue=5 |pages=362–367 |doi=10.7326/M20-3012 |issn=1539-3704 |pmc=7281624 |pmid=32491919}}</ref> Large genetic studies have defined risk factors for severe SARS-CoV-2 infections, and [[Genome|genome sequences]] from 659 patients with severe COVID-19 revealed genetic variants that appear to be associated with life-threatening disease. One gene identified in these studies is type I [[Interferon type I|interferon]] (IFN). Autoantibodies against type I IFNs were found in up to 13.7% of patients with life-threatening COVID-19, indicating that a complex interaction between genetics and the [[immune system]] is important for natural resistance to Covid.<ref>{{Cite journal |last1=Beck |first1=David B. |last2=Aksentijevich |first2=Ivona |date=2020-10-23 |title=Susceptibility to severe COVID-19 |journal=Science |language=en |volume=370 |issue=6515 |pages=404–405 |doi=10.1126/science.abe7591 |pmid=33093097 |s2cid=225041500 |issn=0036-8075|doi-access=free }}</ref>

Similarly, mutations in the [[ERAP2]] gene, encoding endoplasmic reticulum aminopeptidase 2, seem to increase the susceptibility to the [[Plague (disease)|plague]], the disease caused by an infection with the bacteria ''[[Yersinia pestis]]''. People who inherited two copies of a complete variant of the gene were twice as likely to have survived the plague as those who inherited two copies of a truncated variant.<ref>{{Cite journal |last1=Klunk |first1=Jennifer |last2=Vilgalys |first2=Tauras P. |last3=Demeure |first3=Christian E. |last4=Cheng |first4=Xiaoheng |last5=Shiratori |first5=Mari |last6=Madej |first6=Julien |last7=Beau |first7=Rémi |last8=Elli |first8=Derek |last9=Patino |first9=Maria I. |last10=Redfern |first10=Rebecca |last11=DeWitte |first11=Sharon N. |last12=Gamble |first12=Julia A. |last13=Boldsen |first13=Jesper L. |last14=Carmichael |first14=Ann |last15=Varlik |first15=Nükhet |date=November 2022 |title=Evolution of immune genes is associated with the Black Death |journal=Nature |volume=611 |issue=7935 |pages=312–319 |doi=10.1038/s41586-022-05349-x |issn=1476-4687 |pmc=9580435 |pmid=36261521|bibcode=2022Natur.611..312K }}</ref>

Susceptibility also determined the epidemiology of infection, given that different populations have different genetic and environmental conditions that affect infections.