Measles

Measles disease virus, characterized by a single helical RNA chain with negative polarity, belongs to the Measles Morbillivirus species of the genus Morbillivirus.
Under the microscope it appears to be 100 to 250 nm in diameter, where the genome is enclosed by a nucleocapsid, which in turn is lined by a lipid bilayer to which two glycosylated proteins are inserted; Hemagglutinin, responsible for adhesion to target cells, and Fusion Protein, which ensures fusion with the cell membrane of susceptible cells.
Humans represent the sole reservoir of the virus, where it lodges in the respiratory tract and is excreted in nasopharyngeal secretions. The virus appears to be poorly resistant to chemical and physical agents, while in the droplets by which it is eliminated from the diseased individual it can persist in the air for 2 hours and consequently infect other people.

Measles is transmitted by air, mainly by droplets (small particles emitted from the respiratory system during coughing, sneezing or even just talking) over short distances, usually less than 1 meter.
Also not to be overlooked is the possibility that measles can be transmitted by aerosol particles. In particular situations, such as in a poorly ventilated room, the virus can survive for about 2 hours by infecting susceptible people who inhale air containing the virus.

Measles is one of the most contagious diseases in the world with an endemic pattern. This means that it is continuously present in the community, infecting susceptible people, who subsequently develop a permanent immunity to the disease after an initial infection.
In the pre-vaccine era, measles claimed numerous lives worldwide. Occurring as epidemics about every 2-3 years it caused 2.6 million deaths each year, according to WHO data.
Only thanks to the discovery of the vaccine and vaccine immunization, which started in 1960, has the epidemic picture changed dramatically. From WHO's analysis of the latest published data, the measles mortality rate between 2000 and 2018 has declined significantly, with a 73 percent decrease worldwide. Approximately 23.2 million lives were saved during this period.
Unfortunately, despite the availability for more than 50 years of the vaccine, measles remains a leading cause of death in the child population, particularly in children under the age of 5. In 2018, 140,000 measles deaths were recorded globally, most of them children.
Nationally, measles from 1970 until the 1990s presented rather high epidemic peaks. With the introduction of vaccination and particularly the increase in vaccination coverage since 2000, cases have been steadily declining, but not in line with WHO and National Measles Elimination Plan goals. According to a recently published study, Italy could not meet the goal of eliminating measles by 2015, but in contrast, cases increased slightly between 2014 and 2015. It is speculated that this increase is due to the circulation of new imported strains related to international travel.

The symptoms of measles begin to manifest on average about 10 days after exposure to the source of infection, but the incubation period can vary from a minimum of 7 to a maximum of 18 days.

The clinical manifestation of the disease can be distinguished into 3 phases:

• The prodromal or mucositis or catarrhal phase: lasts about 4-5 days, characterized by the onset of fever, cold, involvement of the oral, conjunctival and nasal mucous membranes with production of phlegm. Infected individuals may complain of photophobia, i.e., sensitivity to light sources, congested eyes and lacrimation. At the level of the oral cavity, the mucosa appears reddened and swollen, while observing the soft palate reveals small petechiae. Around the second or third day of the prodromal phase, whitish punctiform elements typical of measles disease known as "Koplik's spots" appear, which disappear within 1 to 2 days.
• The exanthematous phase: lasts about 4 to 5 days, characterized by the appearance of a red papular macular exanthem evolving cranio-caudally. It starts from the retro-auricular region and the nape of the neck and then spreads to the face, trunk and upper limbs and then to the rest of the body causing itching. These spots after about 24/48 hours tend to converge forming a single patch taking on a darker color. Fever in this phase continues to persist, and modest swelling of the posterior angle-mandibular and cervical lymph nodes may be noted.
• The convalescent phase: i.e., the phase of disease resolution, the rash in this phase tends to regress in the same direction as its onset, thus in a cranio-caudal direction. It leaves a tendentially brownish coloration accompanied by dandruff-like scaling and disappearance of fever.

Overall, measles resolves of within about three weeks, with a benign course, causing permanent immunity over time. In some cases, however, the infection can evolve into very severe clinical forms, especially in at-risk individuals. Complications of measles occur in about 30 percent of cases with sometimes particularly severe consequences. Most complications are due to bacterial superinfections in the respiratory system such as; otitis, laryngitis, bacterial bronchopneumonia, and interstitial pneumonia. An additional known complication of measles is diarrhea. Neurological complications can also occur such as encephalitis, causing intellectual disability, or subacute sclerosing encephalitis, a fatal but very rare condition that occurs years after the illness (about 7/10 years). Other complications include those affecting the cardiac, ocular, and immune systems (plateletopenia). The virus, by attacking the immune system, results in a depression of cellular immunity that can cause reactivation of latent tuberculosis. Several studies have shown that in some individuals the virus is capable of causing damage to our immune system making it more vulnerable to infections that normally do not do serious damage, such as influenza. Not to be forgotten are the complications of measles in pregnant women, where it is associated with a risk of miscarriage, premature births and intrauterine death, the latter of which increases when infection occurs during the first and second trimesters of pregnancy. Near delivery in vece increases the risk of neonatal measles.

The diagnosis of measles is ascertained by clinical evaluation of the patient's symptoms. Koplik's spots are a typical sign of measles disease leading to its diagnosis during the prodromal phase.
Laboratory investigations can be performed for measles-specific immunoglobulins of class IgM that appear approximately 1-2 days after the rash, indicating an ongoing infection.
Another possibility for diagnosis is based on the search for the virus in respiratory secretions by the Polymerase Chain Reaction (PCR) technique.

To date, there is no specific treatment for measles. The only available treatment is supportive care to relieve the symptoms of the disease by ensuring good hydration especially in cases of diarrhea and administration of an antipyretic for fever.
The use of an antiviral drug, ribavirin, in immunocompromised individuals with very severe complications from measles has been tested, but it is considered an experimental drug.
WHO recommends the administration of vitamin A in people with measles, especially children, because it has been shown that in cases of malnutrition and deficiency of this vitamin, the risk of measles complications increases.

The only effective weapon against measles disease is the vaccine, which is considered among the safest and most effective vaccines that provides long-lasting immunity. It is a mandatory vaccine that is administered in the form of a trivalent or tetravalent vaccine. The trivalent prevents measles, mumps and rubella infections called MPR, while, the quadrivalent prevents infections against measles, mumps, rubella and varicella also called MPRV.