Editing Group A streptococcal infection (section)

==Types of infection==
Group A β-hemolytic streptococcus can cause infections of the throat and skin.<ref>{{cite web|title=Group A Streptococcal (GAS) Disease|url=https://www.cdc.gov/groupastrep/index.html|website=Centers for Disease Control and Prevention|publisher=U.S. Department of Health & Human Services|access-date=21 November 2012}}</ref>  These may vary from very mild conditions to severe, life-threatening diseases.  Although it is not completely clear what causes different people to develop different diseases as a result of infection with the same [[pathogenic bacteria]], it is suspected that host [[phenotypic]] and [[epigenetic]] factors are the source of such variation. Indeed, the many [[virulence factor]]s of GAS can influence the epigenetics of the host.  Furthermore, persons with suppressed or compromised [[immune system]]s may be more susceptible to certain diseases caused by GAS than other persons with intact immune systems. A 2019 study shows that GAS's evasion of immune detection is facilitated by protein''&nbsp;''S, an extracellular and cell wall-associated protein that enables it to camouflage itself by binding fragments of lysed red blood cells.<ref>{{cite journal|title=Group A Streptococcal S Protein Utilizes Red Blood Cells as Immune Camouflage and Is a Critical Determinant for Immune Evasion|year=2019 |pmid=31801066 |last1=Wierzbicki |first1=I. H. |last2=Campeau |first2=A. |last3=Dehaini |first3=D. |last4=Holay |first4=M. |last5=Wei |first5=X. |last6=Greene |first6=T. |last7=Ying |first7=M. |last8=Sands |first8=J. S. |last9=Lamsa |first9=A. |last10=Zuniga |first10=E. |last11=Pogliano |first11=K. |last12=Fang |first12=R. H. |last13=Larock |first13=C. N. |last14=Zhang |first14=L. |last15=Gonzalez |first15=D. J. |journal=Cell Reports |volume=29 |issue=10 |pages=2979–2989.e15 |doi=10.1016/j.celrep.2019.11.001 |pmc=6951797 }}</ref>

Humans may also carry the GAS either on the [[skin]] or in the [[throat]] and show no symptoms.<ref name="nyc.gov">{{cite web|title=Streptococcal Infections (Invasive Group A Srtep) |url=http://www.nyc.gov/html/doh/html/cd/cdstrep.shtml |publisher=New York City Department of Health a |access-date=21 November 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121106194414/http://www.nyc.gov/html/doh///html/cd/cdstrep.shtml |archive-date=6 November 2012 }}</ref> These carriers are less contagious than symptomatic carriers of the bacteria.<ref name="nyc.gov"/>

The non-invasive infections caused by GAS tend to be less severe and more common.  They occur when the bacteria colonizes the throat area, where it recognizes [[epithelial cells]].<ref>{{cite web|title=Streptococcal Infections: What is Group A Strepotococcus (GAS) |url=http://www.medicinenet.com/streptococcal_infections/page2.htm |access-date=21 November 2012}}</ref>  The two most prominent infections of GAS are both non-invasive: [[strep throat]] ([[pharyngitis]]) where it causes 15–30% of the childhood cases and 10% of adult cases, and [[impetigo]].<ref name="Cohen-Poradosu 2007"/>  These may be effectively treated with antibiotics. [[Scarlet fever]] is also a non-invasive infection caused by GAS, although much less common.

The invasive infections caused by Group A β-hemolytic streptococcus tend to be more severe and less common.  These occurs when the bacterium is able to infect areas where bacteria are not usually found, such as [[blood]] and [[Organ (anatomy)|organ]]s.<ref name="nyc.gov"/> The diseases that may be caused as a result of this include streptococcal [[toxic shock syndrome]] (STSS), [[necrotizing fasciitis]] (NF), [[pneumonia]], and [[bacteremia]].<ref name="Cohen-Poradosu 2007"/> 
 
In addition, infection of GAS may lead to further complications and health conditions, namely acute [[rheumatic fever]] and poststreptococcal [[glomerulonephritis]].

'''Most common:'''
* [[impetigo]], [[cellulitis]], and [[erysipelas]] – infections of the [[skin]] which can be complicated by [[necrotizing fasciitis]] – [[skin]], [[fascia]] and [[muscle]] 
* [[strep throat]] AKA strep pharyngitis – [[pharynx]]

'''Less common:'''
* [[bacteremia]] can be associated with these infections, but is not typical.  
* [[septic arthritis]] – [[joint]]s
* [[osteomyelitis]] – [[bone]]s
* [[vaginitis]] – [[vagina]] (more common in pre-pubescent girls)
* [[meningitis]]* – [[meninges]] 
* [[sinusitis]]* – [[sinuses]]
* [[pneumonia]]* – [[pulmonary alveolus]]

(*Note that meningitis, sinusitis and pneumonia can all be caused by Group A Strep, but are ''much'' more commonly associated with ''[[Streptococcus pneumoniae]]'' and should not be confused.)

===Severe infections===
Some strains of group A streptococci (GAS) cause severe infection. Severe infections are usually invasive, meaning that the [[bacteria]] has entered parts of the body where bacteria are not usually found, such as the [[blood]], [[lung]]s, deep [[muscle]] or [[fat tissue]].<ref>{{cite web|title=Streptococcal Infections (Invasive Group A Strep) |url=http://www.nyc.gov/html/doh/html/cd/cdstrep.shtml |publisher=New York City Department of Health and Mental Hygiene |access-date=November 21, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121106194414/http://www.nyc.gov/html/doh///html/cd/cdstrep.shtml |archive-date=November 6, 2012 }}</ref> Those at greatest risk include children with [[chickenpox]]; persons with [[suppressed immune systems]]; [[burn victims]]; elderly persons with [[cellulitis]], [[diabetes]], [[vascular disease]], or [[cancer]]; and persons taking [[steroid]] treatments or [[chemotherapy]]. [[Intravenous drug]] users and homeless also are at high risk.<ref>{{cite journal  |vauthors=Zangarini L, Martiny D, Miendje Deyi VY, Hites M, Maillart E, Hainaut M, Delforge M, Botteaux A, Matheeussen V, Goossens H, Hallin M, Smeesters P, Dauby N | year = 2023 | title = Incidence and clinical and microbiological features of invasive and probable invasive streptococcal group A infections in children and adults in the Brussels-Capital Region, 2005–2020 | journal = Eur J Clin Microbiol Infect Dis
 | volume = 42 | issue = 5| pages = 555–567 | doi=10.1007/s10096-023-04568-y| pmid = 36881216 | doi-access = free | pmc = 9989989 }}</ref> GAS is an important cause of [[puerperal fever]] worldwide, causing serious infection and, if not promptly diagnosed and treated, death in newly delivered mothers. Severe GAS disease may also occur in healthy persons with no known risk factors.

All severe GAS infections may lead to [[Shock (circulatory)|shock]], [[multisystem organ failure]], and [[death]]. Early recognition and treatment are critical.<ref name=NYT71112>{{cite news|title=An Infection, Unnoticed, Turns Unstoppable|url=https://www.nytimes.com/2012/07/12/nyregion/in-rory-stauntons-fight-for-his-life-signs-that-went-unheeded.html|access-date=July 12, 2012|newspaper=The New York Times|date=July 11, 2012|author=Jim Dwyer}}</ref><ref name=NYT71812>{{cite news|title=After Boy's Death, Hospital Alters Discharging Procedures|url=https://www.nytimes.com/2012/07/19/nyregion/after-rory-stauntons-death-hospital-alters-discharge-procedures.html|access-date=July 19, 2012|newspaper=The New York Times|date=July 18, 2012|author=Jim Dwyer}}</ref> Diagnostic tests include [[blood counts]] and [[urinalysis]] as well as cultures of blood or fluid from a wound site.

Severe Group A streptococcal infections often occur sporadically but can be spread by person-to-person contact.<ref>{{cite journal  |vauthors=Gamba MA, Martinelli M, Schaad HJ, Streuli RA, DiPersio J, Matter L, etal | year = 1997 | title = Familial transmission of a serious disease producing group A streptococcus clone:case reports and review | journal = Clin Infect Dis | volume = 24 | issue = 6| pages = 1118–21 | doi=10.1086/513636| pmid = 9195067 | doi-access = free }}</ref> Close contacts of people affected by severe Group A streptococcal infections, defined as those having had prolonged household contact in the week before the onset of illness, may be at increased [[risk of infection]]. This increased risk may be due to a combination of shared genetic susceptibility within the family, close contact with carriers, and the virulence of the Group A streptococcal strain that is involved.<ref name="hpa.org.uk">{{cite journal | author = Health Protection Agency, Group A Streptococcus Working Group | year = 2004 | title = Interim UK guidelines for management of close community contacts of invasive group A streptococcal disease | url = http://www.hpa.org.uk/cdph/issues/CDPHVol7/no4/guidelines1_4_04.pdf | journal = Commun Dis Public Health | volume = 7 | issue = 4 | pages = 354–61 | access-date = 2008-05-09 | archive-url = https://web.archive.org/web/20080625212441/http://www.hpa.org.uk/cdph/issues/CDPHVol7/no4/guidelines1_4_04.pdf | archive-date = 2008-06-25 | url-status = dead | pmid = 15786581 }}</ref>

[[Public health]] policies internationally reflect differing views of how the close contacts of people affected by severe Group A streptococcal infections should be treated. [[Health Canada]]<ref>Guidelines for management of contacts of cases of invasive group A streptococcal disease (GAS) including streptococcal toxic shock syndrome (STSS) and necrotising fasciitis. Toronto, Ontario: Ministry of Health; 1995. Available at: [https://web.archive.org/web/20030324040345/http://microbiology.mtsinai.on.ca/protocols/pdf/k5b.pdf]</ref> and the US CDC recommend close contacts see their doctor for full evaluation and may require antibiotics;<ref>{{cite web|url=https://www.cdc.gov/ncidod/dbmd/diseaseinfo/groupastreptococcal_g.htm |title=Disease Listing, Group a Streptococcal, General Info &#124; CDC Bacterial, Mycotic Diseases |access-date=2007-12-11 |url-status=dead |archive-url=https://web.archive.org/web/20071219224215/http://www.cdc.gov/ncidod/dbmd/diseaseinfo/groupastreptococcal_g.htm |archive-date=2007-12-19 }}</ref> current UK [[Health Protection Agency]] guidance is that, for a number of reasons, close contacts should not receive antibiotics unless they are symptomatic but that they should receive information and advice to seek immediate medical attention if they develop symptoms.<ref name="hpa.org.uk"/> However, guidance is clearer in the case of mother-baby pairs: both mother and baby should be treated if either develops an invasive GAS infection within the first 28 days following birth<ref name="hpa.org.uk"/> (though some evidence suggests that this guidance is not routinely followed in the UK<ref>{{cite journal |last1=Howard |first1=SJ |last2=Stoker |first3=K |last3=Foster |first2=K |date=16 June 2015 |title=Public health management of group A streptococcal infection in mother-baby pairs in England; a case series review |journal=Antimicrobial Resistance and Infection Control |volume=4 |issue=Suppl 1 |doi=10.1186/2047-2994-4-S1-P107 |pages=P107|pmc=4474978 |doi-access=free }}</ref>).

According to a 2025 study published in ''[[JAMA]]'', cases of invasive group A streptococcal infections more than doubled between 2013 and 2022, following nearly two decades of stable rates.<ref>{{Cite journal |last=Gregory |first=Christopher J. |last2=Okaro |first2=Jennifer Onukwube |last3=Reingold |first3=Arthur |last4=Chai |first4=Shua |last5=Herlihy |first5=Rachel |last6=Petit |first6=Susan |last7=Farley |first7=Monica M. |last8=Harrison |first8=Lee H. |last9=Como-Sabetti |first9=Kathy |last10=Lynfield |first10=Ruth |last11=Snippes Vagnone |first11=Paula |last12=Sosin |first12=Daniel |last13=Anderson |first13=Bridget J. |last14=Burzlaff |first14=Kari |last15=Martin |first15=Tasha |date=2025-04-07 |title=Invasive Group A Streptococcal Infections in 10 US States |url=https://jamanetwork.com/journals/jama/article-abstract/2832277?&utm_source=BulletinHealthCare&utm_medium=email&utm_term=040825&utm_content=NON-MEMBER&utm_campaign=article_alert-morning_rounds_daily&utm_uid=5590102&utm_effort=DAMR01 |journal=JAMA |doi=10.1001/jama.2025.0910 |issn=0098-7484|url-access=subscription }}</ref> Researchers suggest a combination of factors may be contributing to this surge, including higher rates of [[diabetes]] and obesity that weaken immune defenses, increased incidence among individuals who use injectable drugs or face homelessness, and the emergence of new bacterial strains that may be more infectious or resistant to antibiotics.<ref>{{Cite web |date=2025-04-07 |title=Invasive strep infections have more than doubled in the U.S., CDC study finds |url=https://www.nbcnews.com/health/health-news/invasive-strep-infections-doubled-us-cdc-study-finds-rcna199759 |access-date=2025-04-13 |website=NBC News |language=en}}</ref> The findings highlight an urgent need for stronger prevention and control strategies.