Editing Infection (section)

==Prevention==
{{main|Public health|Infection control}}
[[File:OCD handwash.jpg|thumb|right|Washing one's hands, a form of [[hygiene]], is an effective way to prevent the spread of infectious disease.<ref name=handhygiene>{{cite journal|vauthors=Bloomfield SF, Aiello AE, Cookson B, O'Boyle C, Larson EL|url=http://www.ajicjournal.org/article/S0196-6553(07)00595-0/fulltext|title=The effectiveness of hand hygiene procedures including hand-washing and alcohol-based hand sanitizers in reducing the risks of infections in home and community settings|journal=American Journal of Infection Control|year=2007|volume=35|issue=10|pages=S27–S64|doi=10.1016/j.ajic.2007.07.001|pmc=7115270|access-date=2017-03-26|archive-date=2020-06-19|archive-url=https://web.archive.org/web/20200619195845/https://www.ajicjournal.org/article/S0196-6553(07)00595-0/fulltext|url-status=live}}</ref>]]
Techniques like hand washing, wearing gowns, and wearing face masks can help prevent infections from being passed from one person to another. [[Asepsis|Aseptic technique]] was introduced in medicine and surgery in the late 19th century and greatly reduced the incidence of infections caused by surgery. Frequent [[hand washing]] remains the most important defense against the spread of unwanted organisms.<ref>{{cite web|url=http://science.education.nih.gov/supplements/nih1/diseases/guide/fig4-longdesc.htm|title="Generalized Infectious Cycle" Diagram Illustration|website=science.education.nih.gov|access-date=2010-01-21|archive-url=https://web.archive.org/web/20090924155114/https://science.education.nih.gov/supplements/nih1/diseases/guide/fig4-longdesc.htm|archive-date=2009-09-24}}</ref> There are other forms of prevention such as avoiding the use of illicit drugs, using a [[condom]], wearing gloves, and having a healthy lifestyle with a balanced diet and regular exercise. Cooking foods well and avoiding foods that have been left outside for a long time is also important.{{cn|date=April 2023}}

[[Antimicrobials|Antimicrobial substances]] used to prevent transmission of infections include:{{cn|date=April 2023}}
* [[antiseptics]], which are applied to living [[biological tissue|tissue]]/[[skin]]
* [[disinfectant]]s, which destroy microorganisms found on non-living objects.
* [[antibiotic]]s, called [[prophylactic]] when given as prevention rather as treatment of infection. However, long term use of antibiotics leads to resistance of bacteria. While humans do not become immune to antibiotics, the bacteria does. Thus, avoiding using antibiotics longer than necessary helps preventing bacteria from forming mutations that aide in antibiotic resistance.

One of the ways to prevent or slow down the transmission of infectious diseases is to recognize the different characteristics of various diseases.<ref name=Watts>{{cite book |author=Watts, Duncan |title=Six degrees: the science of a connected age |publisher=William Heinemann |location=London |year=2003 |isbn=978-0-393-04142-2 |url-access=registration |url=https://archive.org/details/sixdegrees00dunc }}</ref> Some critical disease characteristics that should be evaluated include [[virulence]], distance traveled by those affected, and level of contagiousness. The human strains of [[Ebola]] virus, for example, incapacitate those infected extremely quickly and kill them soon after. As a result, those affected by this disease do not have the opportunity to travel very far from the initial infection zone.<ref>{{cite book |author=Preston, Richard |title=The hot zone |publisher=Anchor Books |location=Garden City, N.Y. |year=1995 |isbn=978-0-385-49522-6 }}</ref> Also, this virus must spread through skin lesions or permeable membranes such as the eye. Thus, the initial stage of [[Ebola]] is not very contagious since its victims experience only internal hemorrhaging. As a result of the above features, the spread of Ebola is very rapid and usually stays within a relatively confined geographical area. In contrast, the [[human immunodeficiency virus]] ([[HIV]]) kills its victims very slowly by attacking their immune system.<ref name=Sherris>{{cite book |veditors=Ryan KJ, Ray CG | title = Sherris Medical Microbiology | edition = 4th | publisher = McGraw Hill | year = 2004 | isbn = 978-0-8385-8529-0 }}</ref> As a result, many of its victims transmit the virus to other individuals before even realizing that they are carrying the disease. Also, the relatively low virulence allows its victims to travel long distances, increasing the likelihood of an [[epidemic]].{{cn|date=April 2023}}

Another effective way to decrease the transmission rate of infectious diseases is to recognize the effects of [[small-world networks]].<ref name=Watts/> In epidemics, there are often extensive interactions within hubs or groups of infected individuals and other interactions within discrete hubs of susceptible individuals. Despite the low interaction between discrete hubs, the disease can jump and spread in a susceptible hub via a single or few interactions with an infected hub. Thus, infection rates in small-world networks can be reduced somewhat if interactions between individuals within infected hubs are eliminated (Figure 1). However, infection rates can be drastically reduced if the main focus is on the prevention of transmission jumps between hubs. The use of needle exchange programs in areas with a high density of drug users with HIV is an example of the successful implementation of this treatment method.<ref>{{Cite book |last1=Programs |first1=National Research Council (US) and Institute of Medicine (US) Panel on Needle Exchange and Bleach Distribution |url=https://www.ncbi.nlm.nih.gov/books/NBK232343/ |title=The Effects of Needle Exchange Programs |last2=Normand |first2=Jacques |last3=Vlahov |first3=David |last4=Moses |first4=Lincoln E. |date=1995 |publisher=National Academies Press (US) |language=en |access-date=2022-10-20 |archive-date=2021-03-10 |archive-url=https://web.archive.org/web/20210310033308/https://www.ncbi.nlm.nih.gov/books/NBK232343/ |url-status=live }}</ref> Another example is the use of ring culling or vaccination of potentially susceptible livestock in adjacent farms to prevent the spread of the [[foot-and-mouth]] virus in 2001.<ref>{{cite journal | vauthors = Ferguson NM, Donnelly CA, Anderson RM | title = The foot-and-mouth epidemic in Great Britain: pattern of spread and impact of interventions | journal = Science | volume = 292 | issue = 5519 | pages = 1155–60 | date = May 2001 | pmid = 11303090 | doi = 10.1126/science.1061020 | bibcode = 2001Sci...292.1155F | s2cid = 16914744 | doi-access = free }}</ref>

A general method to prevent transmission of [[vector (epidemiology)|vector]]-borne pathogens is [[pest control]].

In cases where infection is merely suspected, individuals may be [[quarantined]] until the incubation period has passed and the disease manifests itself or the person remains healthy. Groups may undergo quarantine, or in the case of communities, a [[Cordon sanitaire (medicine)|cordon sanitaire]] may be imposed to prevent infection from spreading beyond the community, or in the case of [[protective sequestration]], into a community. Public health authorities may implement other forms of [[social distancing]], such as school closings, [[lockdown]]s or temporary restrictions (e.g. [[2020–21 Singapore circuit breaker measures|circuit breakers]])<ref>{{Citation |last=von Csefalvay |first=Chris |title=Modeling the control of infectious disease |date=2023 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780323953894000153 |work=Computational Modeling of Infectious Disease |pages=173–215 |publisher=Elsevier |language=en |doi=10.1016/b978-0-32-395389-4.00015-3 |isbn=978-0-323-95389-4 |access-date=2023-03-02 |archive-date=2023-03-05 |archive-url=https://web.archive.org/web/20230305033759/https://linkinghub.elsevier.com/retrieve/pii/B9780323953894000153 |url-status=live }}</ref> to control an epidemic.

===Immunity===
[[File:Mallon-Mary 01.jpg|thumb|[[Mary Mallon]] (a.k.a. Typhoid Mary) was an asymptomatic carrier of [[typhoid fever]]. Over the course of her career as a cook, she infected 53 people, three of whom died.]]
Infection with most pathogens does not result in death of the host and the offending organism is ultimately cleared after the symptoms of the disease have waned.<ref name= Baron/> This process requires [[immune system|immune mechanisms]] to kill or inactivate the [[Inoculation|inoculum]] of the pathogen. Specific acquired [[immunity (medical)|immunity]] against infectious diseases may be mediated by [[Antibody|antibodies]] and/or [[T lymphocyte]]s. Immunity mediated by these two factors may be manifested by:
* a direct effect upon a pathogen, such as antibody-initiated [[complement system|complement]]-dependent bacteriolysis, [[Opsonin|opsonoization]], [[phagocytosis]] and killing, as occurs for some bacteria,
* neutralization of viruses so that these organisms cannot enter cells,
* or by T lymphocytes, which will kill a cell parasitized by a microorganism.

The immune system response to a microorganism often causes symptoms such as a high [[fever]] and [[inflammation]], and has the potential to be more devastating than direct damage caused by a microbe.<ref name=Sherris/>

Resistance to infection ([[immunity (medical)|immunity]]) may be acquired following a disease, by [[asymptomatic carrier|asymptomatic carriage]] of the pathogen, by harboring an organism with a similar structure (crossreacting), or by [[vaccination]]. Knowledge of the protective antigens and specific acquired host immune factors is more complete for primary pathogens than for [[opportunistic pathogen]]s. There is also the phenomenon of [[herd immunity]] which offers a measure of protection to those otherwise vulnerable people when a large enough proportion of the population has acquired immunity from certain infections.<ref name="ofg">{{cite web |title=Herd Immunity |url=http://vk.ovg.ox.ac.uk/herd-immunity |url-status=live |archive-url=https://web.archive.org/web/20190802220355/http://vk.ovg.ox.ac.uk/herd-immunity |archive-date=2 August 2019 |access-date=11 August 2023 |publisher=Oxford Vaccine Group, University of Oxford}}</ref>

Immune resistance to an infectious disease requires a critical level of either antigen-specific antibodies and/or T cells when the host encounters the pathogen. Some individuals develop natural [[blood plasma|serum]] antibodies to the surface [[polysaccharide]]s of some agents although they have had little or no contact with the agent, these natural antibodies confer specific protection to adults and are [[passive immunization|passively transmitted]] to newborns.

====Host genetic factors====
The organism that is the target of an infecting action of a specific infectious agent is called the host. The host harbouring an agent that is in a mature or sexually active stage phase is called the definitive host. The intermediate host comes in contact during the larvae stage. A host can be anything living and can attain to asexual and sexual reproduction.<ref>{{cite journal|vauthors=Barreto ML, Teixeira MG, Carmo EH|year=2006|title=Infectious diseases epidemiology|journal=Journal of Epidemiology and Community Health|volume=60|issue=3|pages=192–95|doi=10.1136/jech.2003.011593|pmc=2465549|pmid=16476746}}</ref>
The clearance of the pathogens, either treatment-induced or spontaneous, it can be influenced by the genetic variants carried by the individual patients. For instance, for genotype 1 [[hepatitis C]] treated with [[Pegylated interferon-alpha-2a]] or [[Pegylated interferon-alpha-2b]] (brand names Pegasys or PEG-Intron) combined with [[ribavirin]], it has been shown that genetic polymorphisms near the human IL28B gene, encoding interferon lambda 3, are associated with significant differences in the treatment-induced clearance of the virus. This finding, originally reported in ''[[Nature (journal)|Nature]]'',<ref>{{cite journal |vauthors=Ge D, Fellay J, Thompson AJ, Simon JS, Shianna KV, Urban TJ, Heinzen EL, Qiu P, Bertelsen AH, Muir AJ, Sulkowski M, McHutchison JG, Goldstein DB | title = Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance | journal = Nature | volume = 461 | issue = 7262 | pages = 399–401 | year = 2009 | pmid = 19684573 | doi = 10.1038/nature08309 | bibcode = 2009Natur.461..399G | s2cid = 1707096 }}</ref> showed that genotype 1 hepatitis C patients carrying certain genetic variant alleles near the IL28B gene are more possibly to achieve sustained virological response after the treatment than others. Later report from ''Nature''<ref>{{cite journal |vauthors=Thomas DL, Thio CL, Martin MP, Qi Y, Ge D, O'Huigin C, Kidd J, Kidd K, Khakoo SI, Alexander G, Goedert JJ, Kirk GD, Donfield SM, Rosen HR, Tobler LH, Busch MP, McHutchison JG, Goldstein DB, Carrington M | title = Genetic variation in IL28B and spontaneous clearance of hepatitis C virus | journal = Nature | volume = 461 | issue = 7265 | pages = 798–801 | year = 2009 | pmid = 19759533 | pmc = 3172006 | doi = 10.1038/nature08463 | bibcode = 2009Natur.461..798T }}</ref> demonstrated that the same genetic variants are also associated with the natural clearance of the genotype 1 hepatitis C virus.