measles measles measles is a highly contagious infectious disease caused by measles virus. symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. initial symptoms typically include fever, often greater than 40 °c (104 °f), cough, runny nose, and inflamed eyes. small white spots known as koplik's spots may form inside the mouth two or three days after the start of symptoms. a red, flat rash which usually starts on the face and then spreads to the rest of the body typically begins three to five days after the start of symptoms. common complications include diarrhea (in 8% of cases), middle ear infection (7%), and pneumonia (6%). these occur in part due to measles-induced immunosuppression. less commonly seizures, blindness, or inflammation of the brain may occur. other names include morbilli, rubeola, red measles, and english measles. both rubella, also known as german measles, and roseola are different diseases caused by unrelated viruses. not to be confused with either rubella or roseola, which are also viral diseases with comparable features. measlesother namesmorbilli, rubeola, red measles, english measlesa child showing a day-four measles rashspecialtyinfectious diseasesymptomsfever, cough, runny nose, inflamed eyes, rashcomplicationspneumonia, seizures, encephalitis, subacute sclerosing panencephalitis, immunosuppression, hearing loss, blindnessusual onset10–12 days after exposureduration7–10 dayscausesmeasles viruspreventionmeasles vaccinetreatmentsupportive carefrequency20 million per yeardeaths140,000+ (2018) measles is an airborne disease which spreads easily from one person to the next through the coughs and sneezes of infected people. it may also be spread through direct contact with mouth or nasal secretions. it is extremely contagious: nine out of ten people who are not immune and share living space with an infected person will be infected. furthermore, measles's reproductive number estimates vary beyond the frequently cited range of 12 to 18. the nih quote this 2017 paper saying: " review in 2017 identified feasible measles r0 values of 3.7–203.3". people are infectious to others from four days before to four days after the start of the rash. while often regarded as a childhood illness, it can affect people of any age. most people do not get the disease more than once. testing for the measles virus in suspected cases is important for public health efforts. measles is not known to occur in other animals. once a person has become infected, no specific treatment is available, although supportive care may improve outcomes. such care may include oral rehydration solution (slightly sweet and salty fluids), healthy food, and medications to control the fever. antibiotics should be prescribed if secondary bacterial infections such as ear infections or pneumonia occur. vitamin a supplementation is also recommended for children. among cases reported in the u.s. between 1985 and 1992, death occurred in only 0.2% of cases, but may be up to 10% in people with malnutrition. most of those who die from the infection are less than five years old. the measles vaccine is effective at preventing the disease, is exceptionally safe, and is often delivered in combination with other vaccines. vaccination resulted in an 80% decrease in deaths from measles between 2000 and 2017, with about 85% of children worldwide having received their first dose as of 2017. measles affects about 20 million people a year, primarily in the developing areas of africa and asia. it is one of the leading vaccine-preventable disease causes of death. in 1980, 2.6 million people died from measles, and in 1990, 545,000 died due to the disease; by 2014, global vaccination programs had reduced the number of deaths from measles to 73,000. despite these trends, rates of disease and deaths increased from 2017 to 2019 due to a decrease in immunization. signs and symptoms maculopapular rash on the abdomen after 3 days of measles infection symptoms typically begin 10–14 days after exposure. the classic symptoms include a four-day fever (the 4 d's) and the three c's—cough, coryza (head cold, fever, sneezing), and conjunctivitis (red eyes)—along with a maculopapular rash. fever is common and typically lasts for about one week; the fever seen with measles is often as high as 40 °c (104 °f). koplik's spots seen inside the mouth are diagnostic for measles, but are temporary and therefore rarely seen. koplik spots are small white spots that are commonly seen on the inside of the cheeks opposite the molars. they appear as "grains of salt on a reddish background." recognizing these spots before a person reaches their maximum infectiousness can help reduce the spread of the disease. the characteristic measles rash is classically described as a generalized red maculopapular rash that begins several days after the fever starts. it starts on the back of the ears and, after a few hours, spreads to the head and neck before spreading to cover most of the body, often causing itching. the measles rash appears two to four days after the initial symptoms and lasts for up to eight days. the rash is said to "stain", changing color from red to dark brown, before disappearing. overall, measles usually resolves after about three weeks. 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). further information: stimson line a filipino baby with measles koplik's spots on the third pre-eruptive day koplik's spots on the day of measles rash complications complications of measles are relatively common, ranging from mild ones such as diarrhea to serious ones such as pneumonia (either direct viral pneumonia or secondary bacterial pneumonia), laryngotracheobronchitis (croup) (either direct viral laryngotracheobronchitis or secondary bacterial bronchitis), otitis media, acute brain inflammation, corneal ulceration (leading to corneal scarring), and in about 1 in 600 unvaccinated infants under 15 months while more rarely in older children and adults, subacute sclerosing panencephalitis, which is progressive and eventually lethal. in addition, measles can suppress the immune system for weeks to months, and this can contribute to bacterial superinfections such as otitis media and bacterial pneumonia. two months after recovery there is a 11–73% decrease in the number of antibodies against other bacteria and viruses. the death rate in the 1920s was around 30% for measles pneumonia. people who are at high risk for complications are infants and children aged less than 5 years; adults aged over 20 years; pregnant women; people with compromised immune systems, such as from leukemia, hiv infection or innate immunodeficiency; and those who are malnourished or have vitamin a deficiency. complications are usually more severe in adults. 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%. in underdeveloped nations with high rates of malnutrition and poor healthcare, fatality rates have been as high as 28%. in immunocompromised persons (e.g., people with aids) the fatality rate is approximately 30%. even in previously healthy children, measles can cause serious illness requiring hospitalization. one out of every 1,000 measles cases progresses to acute encephalitis, which often results in permanent brain damage. one to three out of every 1,000 children who become infected with measles will die from respiratory and neurological complications. cause an electron micrograph of the measles virus measles is caused by the measles virus, a single-stranded, negative-sense, enveloped rna virus of the genus morbillivirus within the family paramyxoviridae. the virus is highly contagious and is spread by coughing and sneezing via close personal contact or direct contact with secretions. measles is the most contagious virus known. it remains infective for up to two hours in that airspace or nearby surfaces. measles is so contagious that if one person has it, 90% of non-immune people who have close contact with them (e.g., household members) will also become infected. humans are the only natural hosts of the virus, and no other animal reservoirs are known to exist, although mountain gorillas are believed to be susceptible to the disease. risk factors for measles virus infection include immunodeficiency caused by hiv/aids, immunosuppression following receipt of an organ or a stem cell transplant, alkylating agents, or corticosteroid therapy, regardless of immunization status; travel to areas where measles commonly occurs or contact with travelers from such an area; and the loss of passive, inherited antibodies before the age of routine immunization. pathophysiology drawing of the measles virus attaching to the lining of the trachea once the measles virus gets onto the mucosa, it infects the epithelial cells in the trachea or bronchi. measles virus uses a protein on its surface called hemagglutinin (h protein), to bind to a target receptor on the host cell, which could be cd46, which is expressed on all nucleated human cells, cd150, aka signaling lymphocyte activation molecule or slam, which is found on immune cells like b or t cells, and antigen-presenting cells, or nectin-4, a cellular adhesion molecule. once bound, the fusion, or f protein helps the virus fuse with the membrane and ultimately get inside the cell. as the virus is a single-stranded negative-sense rna virus, it includes the enzyme rna-dependent rna polymerase (rdrp) which is used to transcribe its genome into a positive-sense mrna strand. after entering a cell, it is ready to be translated into viral proteins, wrapped in the cell's lipid envelope, and sent out of the cell as a newly made virus. within days, the measles virus spreads through local tissue and is picked up by dendritic cells and alveolar macrophages, and carried from that local tissue in the lungs to the local lymph nodes. from there it continues to spread, eventually getting into the blood and spreading to more lung tissue, as well as other organs like the intestines and the brain. functional impairment of the infected dendritic cells by the measles virus is thought to contribute to measles-induced immunosuppression. diagnosis typically, clinical diagnosis begins with the onset of fever and malaise about 10 days after exposure to the measles virus, followed by the emergence of cough, coryza, and conjunctivitis that worsen in severity over 4 days of appearing. observation of koplik's spots is also diagnostic. other possible condition that can result in these symptoms include parvovirus, dengue fever, kawasaki disease, and scarlet fever. laboratory confirmation is however strongly recommended. laboratory testing laboratory diagnosis of measles can be done with confirmation of positive measles igm antibodies or detection of measles virus rna from throat, nasal or urine specimen by using the reverse transcription polymerase chain reaction assay. this method is particularly useful to confirm cases when the igm antibodies results are inconclusive. for people unable to have their blood drawn, saliva can be collected for salivary measles-specific iga testing. salivary tests used to diagnose measles involve collecting a saliva sample and testing for the presence of measles antibodies. this method is not ideal, as saliva contains many other fluids and proteins which may make it difficult to collect samples and detect measles antibodies. saliva also contains 800 times fewer antibodies than blood samples do, which makes salivary testing additionally difficult. positive contact with other people known to have measles adds evidence to the diagnosis. prevention further information: measles vaccine, mmr vaccine, and mmrv vaccine rates of measles vaccination worldwide mothers who are immune to measles pass antibodies to their children while they are still in the womb, especially if the mother acquired immunity through infection rather than vaccination. such antibodies will usually give newborn infants some immunity against measles, but these antibodies are gradually lost over the course of the first nine months of life. infants under one year of age whose maternal anti-measles antibodies have disappeared become susceptible to infection with the measles virus. in developed countries, it is recommended that children be immunized against measles at 12 months, generally as part of a three-part mmr vaccine (measles, mumps, and rubella). the vaccine is generally not given before this age because such infants respond inadequately to the vaccine due to an immature immune system. a second dose of the vaccine is usually given to children between the ages of four and five, to increase rates of immunity. measles vaccines have been given to over a billion people. vaccination rates have been high enough to make measles relatively uncommon. adverse reactions to vaccination are rare, with fever and pain at the injection site being the most common. life-threatening adverse reactions occur in less