Measles is a highly contagious childhood infection caused by a virus and results in skin rash and fever. The classification of wild-type measles viruses follows particular genetic categories, called genotypes.

There are 19 to 22 different genotype related to measles virus. Measles virus is called paramyxovirus and transmit mainly through the air or by contact with infectious droplets from the throat, nose, or mouth.

Conditions or characteristics that increase the risk of developing measles include weakened the immune system, traveling internationally, and vitamin a deficiency.

Investigators believe that measles virus attacks the host by infecting the alveolar macrophages and/or dendritic cells in the airways, it then begins to replicate in local lymphoid tissues.Measles signs and symptoms include moderate-to-high fever, skin rash that appears red, blotchy, itchy, and eyes symptoms such as light sensitivity.

A physician may perform a physical exam and ask specific questions regarding the symptoms to diagnose measles properly. A physician is able to diagnose measles merely by examining disease's characteristic rash and by examining the small, bluish-white spots on a bright red on the inside lining of the cheek (Koplik's spots).

There is no specific antiviral drug that can treat measles virus sufficiently. However, taking certain measures to protect individuals who infected with measles virus is advisable.

Measles can lead to more serious complications if not treated such as respiratory infections, ear infections, and blindness. The best protection against measles can be achieved by taking the free measles, mumps and rubella (MMR) vaccine that administered in two doses, one at age 12 to 15 months, and the second at age 5 to 12 years.

From an epidemiological standpoint, 134 200 measles deaths reported in 2015 by WHO and the vast majority of measles deaths occur in countries with low per capita incomes and weak health infrastructures.

Measles is a highly contagious, life-threatening, childhood infection caused by a virus. Measles is very unpleasant disease and can lead to more serious complications. Measles is a serious illness or even fatal for young children, causing a skin rash and fever.

The classification of wild-type measles viruses follows particular genetic categories, called genotypes. The classification of wild-type measles viruses depends on the nucleotide sequences of their hemagglutinin (H) and on the most variable genes on the viral genome (the nucleoprotein (N) genes).

A standard protocol for the designation of measles genotypes has been suggested by the World Health Organization (WHO) in 1998. The 450 nucleotides encoding the carboxy terminus (end of amino acid chain) of the N protein are the minimum amount of sequence data required to assign a virus to a genotype (28).

 The following 19 genotypes have been detected since 1990: A, B2, B3, C1, C2, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, G2, G3, H1, and H2.However, some other studies propose the presence of other genotypes up to  22 genotypes. There is no sufficient evidence to support the notion of biological difference between viruses based on different genotypes or any association of that with the severity of the illness.

A virus dubbed paramyxovirus is responsible for measles and transmit through the air or by contact with infectious droplets from the throat, nose, or mouth. The virus that causes measles multiply in number in the nose and throat of an infected child or adult. The measles virus can be found in numerous of tiny droplets that come out of the nose and mouth when an infected person coughs or sneezes.

Transmission of measles can occur mainly by kissing or by being coughed or sneezed upon by an infected person. According to Centers for Disease Control and Prevention in the US, if one person infected with measles, 90% of the people close to that person who are not immune will also develop the disease. Most people develop measles because they were never immunized against it. If a person gets measles for one time, he/she will be immune for life.

People who at risk for developing measles might have one of the following conditions or characteristics:

• Weakened immune system: Usually due to the presence of HIV infection, congenital immunodeficiency, vaccination in childhood (occurs rarely), or medications that suppress the immune system such as those which prescribed in chemotherapy.
• Traveling internationally: Traveling to developing countries may increase the risk of catching the disease especially in countries where measles is more common.
• Infants who too young to be immunized: Usually in case of those who less than 1 year of age.
• Unvaccinated pregnant women:  Pregnant women who did not get proper immunization against the disease are at high risk of developing measles.
• Unimmunized or unvaccinated individuals: Children and adults who did not get immunization against measles, or who insufficiently immunized at high risk of developing measles.
• Vitamin A deficiency: Consuming improper amount of vitamin A is likely to worsen measles symptoms.

Measles virus (MV) belongs to a genus of viruses called Morbillivirus that descended from Paramyxoviridae family. MV is known to be an enveloped virus with a non-segmented, negative-strand RNA genome. The primary site of infection with measles is the respiratory epithelium of the nasopharynx.  

The observed rash that results from measles occurs simultaneously with substantial evidence of immune activation and followed by an antiviral immune response. This immune response is associated with immune suppression, autoimmune encephalomyelitis, and increased susceptibility to secondary infections, but after all, it is effective in fighting the virus and in establishing long-term resistance to reinfection.

Measles-associated skin rash does not appear in children with T-cell immunodeficiency, the thing which encourages many investigators to believe that skin rash in measles caused mainly by the T-cell response to MV-infected cells in capillary vessels. The mechanisms underlying major features associated with measles such as severe immunosuppression and lymphopenia are not well perceived or understood yet by investigators.

However, infection and subsequent destruction of human signaling lymphocyte activation molecule (SLAM+) cells of the immune system may play a major role in creating such immunological abnormalities. The ideas surrounding pathogenesis of measles have been changed and critically altered by the discovery of new cellular receptors and studies in animal models that conducted during the last 10 or 20 years.

Many investigators believe that measles virus attacks the host by infecting the alveolar macrophages and/or dendritic cells in the airways, it then begins to replicate in local lymphoid tissues. Infected CD150+ lymphocytes will facilitate viremia (spreading of virus in the whole body by blood). Infection of epithelial cells via the newly identified receptor Nectin-4 will be reinforced by infection of lymphocytes and dendritic cells in the respiratory submucosa.

The following are the sequential stages that observed over a period of two to three weeks from measles infection:

• Incubation of infection: From 10 to 14 days after infection happens, the measles virus incubation begins. There is no reports indicate specific signs or symptoms of measles during this time.
• Nonspecific signs and symptoms: The typical signs and symptoms of measles in the first stages are a sore throat, mild to moderate fever (often with a persistent cough), inflamed eyes, and runny nose. This form of mild illness is expected to last two or three days.
• Skin rash and acute illness: The rash seen mostly as small red spots causing splotchy red appearance for the skin. The rash appears firstly on the face, then it spreads down the arms, trunk, thighs, lower legs, and feet. Noticeable fever reported to occur at this time reaching 104 to 105.8 F (40 to 41 C).However, at the end of this stage, the measles rash begins to disappear from the face firstly and last from the thighs and feet.
• Communicable period: It is expected for a person with measles to transmit the virus to other persons for about eight days, starting four days before the appearance of skin rash and ending when the rash has been present for four days.

Measles is associated with recognizable signs and symptoms such as:

• Moderate-to-high fever: The fever begins about 10 to 12 days after infection occurs and lasts 4 to 7 days.
• Cough , sneezing, and runny nose (coryza)
• Irritability , tiredness, and general weakness
• Sore throat, hoarseness, and loss of appetite
• Red spots with bluish-white centers (called Koplik spots) inside the mouth
• Skin rash that appear red, blotchy, itchy and which begins on the face and then spreads. It is common for skin rash to appear 14 days after infection with measles virus occur (within 7 to 18 days). Characteristics of skin rash may include:
• Consist of small, flat, slightly, red-brown spots that may join together into larger raised blotchy patches.
• May observed as flat, discolored areas dubbed macules or as solid, red, raised areas dubbed papules that fused together in the end.
• Often speared on the head or neck, before spreading outwards to the rest of the body.
• May be mistaken with other childhood conditions such as slapped cheek syndrome (fifth disease), roseola, or rubella.
• Improbable to be the result of measles virus if the person has been properly vaccinated.
• Itching is reported in many cases.
• Gastrointestinal symptoms and symptoms that relate to the central nervous system such as diarrhea, vomiting, abdominal pain, extreme drowsiness, seizure, or coma (rare and may occur in 1 in 1,000 cases).
• Eyes symptoms such as light sensitivity (photophobia), swollen eyelids , and Conjunctivitis (red, inflamed eyes)
• Enlarged lymph nodes.

To diagnose measles, a physician may perform a physical exam and ask specific questions regarding the symptoms regarding one’s medical history, immunization and travel history. Laboratory diagnosis of measles may build upon results of:

• Salivary swab or serum sample taken within six weeks of onset to detect measles-specific immunoglobulin M (IgM) (15). Presence of IgM response is transient and range from 1–2 months, but IgG (Immunoglobulin G) response should persist for many years. Uninfected persons should be IgM negative and will be either IgG negative or IgG positive. Previous infection or vaccination history will certainly affect the results of these tests (25)
• Virus RNA detection in salivary swabs or other samples.

A blood test may be suggested by a physician to help confirm the diagnosis and to detect the presence of antibodies that work against measles virus.

The treatment that can get rid of an established measles infection still undiscovered and there is no specific antiviral drug that can treat measles virus sufficiently. The following medications and drugs may be used to manage measles:

• Antipyretics: Those are drugs that reduce fever.Patients can take over-the-counter medications to help relieve the fever that accompanies measles. These medications include acetaminophen, ibuprofen, or naproxen. Parents should be aware of giving aspirin to children under 16 because of the danger of developing Reye syndrome that causes swelling in the liver and brain.
• Antibiotics: Drugs that can treat infections caused by bacteria may be prescribed by physicians in case conditions such as pneumonia and ear infection occur.
• Vitamin A: Investigators assert the notion that people with measles who have low levels of vitamin A are more vulnerable to develop more critical case of measles. Prescribing vitamin A to those people is helpful and can lessen the severity of the disease. Vitamin A is given in large doses to patients with measles, the dose may be administered as 200,000 international units (IU) for two days.

Reliving measles intensity can be achieved by applying certain healthy lifestyle measures and home remedies such as:

• Getting enough rest and avoid intense activities.
• Treating cold-like symptoms and seeking respiratory relief. For instance, it might help children if they sit in a hot, steamy bathroom.
• Treating sore eyes: Crustiness that may be noticed in child's eyelids and lashes can be removed by using cotton wool soaked in water.
• Closing curtains, wearing sunglasses, and avoid reading or watching television if light from a reading lamp or from the television is bothersome.
• Following certain nutritional tips may help reduce symptoms including: 
• Reduce refined foods intake such as white bread and sugar.
• Choose oils that are healthy for cooking, such as olive oil.
• Avoid foods types that contain trans-fatty acids such as cookies, crackers, cakes, and donuts.
• Avoid processed foods, margarine, French fries, and onion rings.
• Avoid alcohol, tobacco, coffee or other stimulants.
• Drink plenty of water and fruit juice.It is advisable to drink 6 to 8 glasses of filtered water daily.
• Treat nutritional deficiencies with by using supplements that include multivitamin (daily), omega-3 fatty acids (such as fish oil), and probiotic supplement (containing Lactobacillus acidophilus).
• Taking certain herbs may contribute in treating measles, herbs may include lingzhi mushroom, green tea, cat’s claw, witch hazel, and Phyllanthus.

Moreover, measles vaccination within 72 hours of exposure to the measles virus can be given to people who unimmunized against measles.

If not managed properly, measles can lead to more serious complications including:

• Shortness of breath and severe respiratory infections such as pneumonia and Bronchitis (swelling and irritation of the main passages that carry air to the lungs).
• The risk of miscarriage, premature labor, and low birth-weight babies can increase if measles develops during pregnancy.
• Seizures and encephalitis (an infection that causes brain swelling).
• A sharp chest pain that worsens with breathing.
• Severe diarrhea and related dehydration.
• Ear infections such as otitis media.
• Drowsiness and confusion.
• Coughing up blood.
• Blindness.

To prevent measles, the two following steps can be carried out: 

• Vaccination: Best protection against measles can be achieved by taking the free measles, mumps, and rubella (MMR) vaccine. Healthcare provider can give MMR vaccine in two separated doses, one at age 12 to 15 months, and the second at age 5 to 12 years.
• Isolation: People with measles should not continue their normal interaction and communication with other people during a period extended from about four days before to four days after the rash breaks out because measles is highly contagious during that period.

Measles severity ranges from mild to severe, usually mild levels can be found in the well-fed children while sever levels can be found in the malnourished or immunosuppressed people.

However, severe cases of measles reported particularly in young adults who have not been vaccinated. The highest rates of severity and mortality have been reported in infancy and lowest rates reported mainly in those aged 1-9 years, before rising again into adulthood.

Acute otitis media is the most common complication that relates to measles in children and mainly reported in 7 to 9% of measles cases. However, complications that involve the respiratory system, central nervous system, or digestive system have been reported in infants and adults, especially those who have weak immune system or who critically malnourished.

Moreover, measles can be fatal in a very small percentage of cases. Pregnant women who exposed to measles are at risk of premature birth, low birth weight babies, miscarriage, and stillbirth.

• The following are measles-related facts published by WHO channels:

• In 2015, there were 134 200 measles deaths, which account for about 367 deaths daily or 15 deaths hourly around the globe.
• Between 2000 and 2015, measles vaccination caused a 79% drop in measles deaths worldwide, prevented an estimated 20.3 million deaths, making measles vaccine one of the best inventions in public health.
• Up to 10% of measles cases result in death in communities with high levels of malnutrition and a lack of adequate health care.
• The vast majority of measles deaths occur in countries with low per capita incomes and weak health infrastructures.
• Reduction in a number of deaths from measles by 50% has been reported in case treating measles with vitamin A supplements.
• During 2015, mass vaccination campaigns in 41 countries took a place and about 183 million children were vaccinated against measles.
• In January 2017, Over 559 measles cases were reported by the WHO European Region. Of these, 474 cases were reported in 7 of the 14 endemic countries (France, Germany, Italy, Poland, Romania, Switzerland and Ukraine).

• The following are measles-related facts published by Centers for Disease Control and Prevention in the US :

• In 1912, measles became a national concern in the United States. An average of 6,000 measles-related deaths were reported each year in the first decade of reporting.
• Before 1963, about 500,000 cases and 500 deaths related to measles were reported every year, with epidemic cycles every 2–3 years. However, the actual estimation of cases exceeded the 3–4 million everywhere.
• The incidence of measles decreased by more than 95% in the years following licensure of the vaccine in 1963 and 2–3-year epidemic cycles stopped from happening.
• Measles was declared eliminated from the United States in 2000 because an absence of continuous disease transmission for greater than 12 months was documented.
• In 2008, 140 cases of measles were reported. About 89% of these cases were associated with importations from other European countries.
• 16 outbreaks of measles and 220 measles cases were reported by CDC in 2011.

• According to European Center for Disease Prevention and Control, in 2015, the total confirmed cases of measles in EU and EEA countries calculated as 2605 cases. Of these, 1588 case reported in Germany. In 2016, the total confirmed cases of measles in EU and EEA countries calculated as 3160 cases. Of these, 1362 case reported in Romania.
• According to a study published in the Journal of Infectious Diseases, from 2000 to 2008, the estimated number of measles deaths decreased by 46% and all South-East Asia countries have achieved the 90% mortality reduction target except India.
• According to a study mentioned in the Communicable Diseases Intelligence journal that published quarterly by the Australian Department of Health, since 1993, reports of measles cases have fallen considerably in Australia. However, between 2000 and 2011, measles cases and hospitalization rates fluctuated. Between 2000 and 2011, there were 990 measles cases in Australia. The most susceptible group were children aged 0–4 years. High incidence was also observed in adolescents and young adults.
• According to a study published in Plos One journal, a total of 18,431 laboratory-confirmed measles cases were reported from all nine provinces of South Africa. Decreasing in measles incidence following the nationwide mass vaccination campaign have been observed even though it was conducted only about one year after the outbreak started.
• A study conducted in the republic of Ghana and published in the East African Medical Journal, confirmed an overall decline in reported cases of measles in the Ghanaian hospitals between 1996 and 2000. Females constituted 48%-52% of the reported 1508 cases in the hospitals.