Editing Measles (section)

==Signs and symptoms==
Symptoms typically begin 7–14 days (typically 11-12 days) after exposure with a [[prodrome]] of fever, [[malaise]], and [[cough]].<ref name="Pink Book" /><ref name="Merck Manual" /><ref name="Rot2016" /> The fever with measles increases in a stepwise fashion and peaks at {{Convert|103|F|C}} - {{Convert|105|F|C}}.<ref name="Pink Book" /> After one to two days of prodromal illness, [[Koplik's spots|Koplik spots]] appear inside the cheeks opposite the molars as clusters of white lesions ("grains of salt") on reddened areas. They are [[pathognomonic]] for measles, but are present for only a short time and therefore are not always seen.<ref name="Merck Manual" /> The classic symptoms include a fever, [[cough]], [[coryza]] (head cold, fever, sneezing), and [[conjunctivitis]], referred to as "the three C's", and a [[maculopapular rash]].<ref name=Biesbroeck2013>{{cite journal | vauthors = Biesbroeck L, Sidbury R | title = Viral exanthems: an update | journal = Dermatologic Therapy | volume = 26 | issue = 6 | pages = 433–8 | date = November 2013 | pmid = 24552405 | doi = 10.1111/dth.12107 | s2cid = 10496269 | doi-access = free | title-link = doi }}</ref>

The characteristic measles [[rash]] is classically described as a generalized red maculopapular rash that begins three to five days after the prodrome; on average, 14 days after exposure, but as few as 7 or as many as 21 days post-exposure.<ref name="Pink Book" /><ref name="Rot2016" /> The rash starts on the back of the ears or on the face and thereafter spreads to the rest of the body. It is caused by the cellular and humoral immune system's clearing of infected skin cells, as is the conjunctivitis. Measles conjunctivitis often also causes [[photophobia]].<ref name="Rot2016" /> The rash is said to "stain", changing color from red to dark brown, before disappearing.

Uncomplicated cases of measles typically improve within days of rash onset and resolve within 7–10 days.<ref name="Rot2016" />

People who have been vaccinated against measles but have incomplete protective immunity may experience a form of modified measles. Modified measles is characterized by a prolonged [[incubation period]], milder, and less characteristic symptoms (sparse and discrete rash of short duration).<ref name="Pink Book" /> Because development of the rash and conjunctivitis requires a functional immune system, immunocompromised people may not be diagnosed as readily.<ref name="Rot2016" /><gallery mode="packed" heights="150" style="text-align:left">
File:Measles child Philippines.jpg|A Filipino baby with measles
File:Koplik spots, measles 6111 lores.jpg|[[Koplik's spots]] on the third pre-eruptive day
File:Morbillivirus measles infection.jpg|Abdominal maculopapular rash on day 3 of illness
</gallery>

===Complications===
Complications of measles are relatively common. Some are caused directly by the virus, while others are caused by viral suppression of the immune system. This phenomenon, known as "immune amnesia", increases the risk of [[Superinfection|secondary bacterial infections]];<ref name="Rot2016" /><ref>{{cite journal |vauthors=Griffin DE |date=July 2010 |title=Measles virus-induced suppression of immune responses |journal=Immunological Reviews |volume=236 |pages=176–89 |doi=10.1111/j.1600-065X.2010.00925.x |pmc=2908915 |pmid=20636817}}</ref><ref name="Amnesia">{{cite web |last=Griffin |first=Ashley Hagen |date=18 May 2019 |title=Measles and Immune Amnesia |url=https://asm.org/Articles/2019/May/Measles-and-Immune-Amnesia |url-status=live |archive-url=https://archive.today/20200118042959/https://asm.org/Articles/2019/May/Measles-and-Immune-Amnesia |archive-date=18 January 2020 |access-date=18 January 2020 |website=asm.org |publisher=American Society for Microbiology}}</ref><ref name="Mina 2019" /> two months after recovery there is an 11–73% decrease in the number of antibodies against other bacteria and viruses.<ref name="Nature">{{cite journal|title=Measles erases immune 'memory' for other diseases|url=https://www.nature.com/articles/d41586-019-03324-7|journal=Nature|access-date=3 November 2019|date=31 October 2019|doi=10.1038/d41586-019-03324-7|last=Guglielmi|first=Giorgia|pmid=33122832|s2cid=208489179|archive-date=2 November 2019|archive-url=https://web.archive.org/web/20191102065033/https://www.nature.com/articles/d41586-019-03324-7|url-status=live|url-access=subscription}}</ref> Population studies from prior to the introduction of the measles vaccine suggest that immune amnesia typically lasts 2–3 years. Primate studies suggest that immune amnesia in measles is effected by replacement of [[Lymphocyte|memory lymphocytes]] with ones that are specific to measles virus, since they are destroyed after being infected by the virus. This creates lasting immunity to measles re-infection, but decreases immunity to other pathogens.<ref name="Amnesia" /> Complications may be directly related to the virus - e.g. [[viral pneumonia]] or viral [[laryngotracheobronchitis]] (croup) - or related to the damage measles virus causes to tissues and the immune system. The most serious direct complications include acute encephalitis,<ref>{{cite journal |vauthors=Fisher DL, Defres S, Solomon T |date=March 2015 |title=Measles-induced encephalitis |journal=QJM |volume=108 |issue=3 |pages=177–82 |doi=10.1093/qjmed/hcu113 |pmid=24865261 | doi-access = free | title-link = doi }}</ref> [[corneal ulcer]]ation (leading to [[corneal abrasion|corneal scarring]]);<ref>{{cite journal |vauthors=Semba RD, Bloem MW |date=March 2004 |title=Measles blindness |journal=Survey of Ophthalmology |volume=49 |issue=2 |pages=243–55 |doi=10.1016/j.survophthal.2003.12.005 |pmid=14998696}}</ref> and [[subacute sclerosing panencephalitis]], a progressive and fatal inflammation of the brain that occurs in about 1 in 600 unvaccinated infants under 15 months. Common secondary infections include [[infectious diarrhea]], [[bacterial pneumonia]], and [[otitis media]].<ref name="Rot2016" />

The death rate in the 1920s was around 30% for measles pneumonia.<ref>{{cite journal | vauthors = Ellison JB | title = Pneumonia in Measles | journal = Archives of Disease in Childhood | volume = 6 | issue = 31 | pages = 37–52 | date = February 1931 | pmid = 21031836 | pmc = 1975146 | doi = 10.1136/adc.6.31.37 }}</ref> People who are at high risk for complications are infants and children aged less than 5 years;<ref name=Medscape2018/> adults aged over 20 years;<ref name=Medscape2018/> pregnant women;<ref name=Medscape2018/> people with compromised immune systems, such as from [[leukemia]], HIV infection or innate immunodeficiency;<ref name=Medscape2018/><ref name="cdc.gov">{{cite web|title=Measles |url=https://www.cdc.gov/measles/hcp/clinical-overview/ |website=U.S. [[Centers for Disease Control and Prevention]] (CDC)|access-date=22 October 2016|url-status=live|archive-url=https://web.archive.org/web/20161023051702/https://www.cdc.gov/measles/hcp/index.html|archive-date=23 October 2016 }}</ref> and those who are [[malnutrition|malnourished]]<ref name=Medscape2018/> or have [[vitamin A deficiency]].<ref name=Medscape2018/><ref>{{cite web|url=https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/|title=Vitamin A|author=National Institutes of Health Office of Dietary Supplements|year=2013|publisher=U.S. Department of Health & Human Services|access-date=11 March 2015|url-status=live|archive-url=https://web.archive.org/web/20150311000932/http://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/|archive-date=11 March 2015}}</ref> Complications are usually more severe in adults.<ref>{{cite journal | vauthors = Sabella C | title = Measles: not just a childhood rash | journal = Cleveland Clinic Journal of Medicine | volume = 77 | issue = 3 | pages = 207–13 | date = March 2010 | pmid = 20200172 | doi = 10.3949/ccjm.77a.09123 | s2cid = 4743168 | doi-access = free | title-link = doi }}</ref> Between 1987 and 2000, the case fatality rate across the United States was three deaths per 1,000 cases attributable to measles, or 0.3%.<ref name="The Clinical Significance of Measles: A Review">{{cite journal | vauthors = Perry RT, Halsey NA | title = The clinical significance of measles: a review | journal = The Journal of Infectious Diseases | volume = 189 Suppl 1 | issue = S1 | pages = S4-16 | date = May 2004 | pmid = 15106083 | doi = 10.1086/377712 | doi-access = free | title-link = doi }}</ref> In [[developing country|underdeveloped nations]] with high rates of malnutrition and poor [[healthcare]], fatality rates have been as high as 28%.<ref name="The Clinical Significance of Measles: A Review"/> In immunocompromised persons (e.g., people with [[AIDS]]) the fatality rate is approximately 30%.<ref name="Sension1988">{{cite journal | vauthors = Sension MG, Quinn TC, Markowitz LE, Linnan MJ, Jones TS, Francis HL, Nzilambi N, Duma MN, Ryder RW | title = Measles in hospitalized African children with human immunodeficiency virus | journal = American Journal of Diseases of Children | volume = 142 | issue = 12 | pages = 1271–2 | date = December 1988 | pmid = 3195521 | doi = 10.1001/archpedi.1988.02150120025021 }}</ref>

Even in previously healthy children, measles can cause serious illness requiring hospitalization.<ref name="cdc.gov"/> One out of every 1,000 measles cases progresses to acute [[encephalitis]], which often results in permanent brain damage.<ref name="cdc.gov"/> One to three out of every 1,000 children who become infected with measles will die from respiratory and neurological complications.<ref name="cdc.gov"/>