Measles

In the US there is a greater than 90% coverages of at least one dose of measles, mumps, and rubella vaccine.

In recent measles outbreaks more than 2/3 of unvaccinated individuals who were eligible for vaccination had a non-medical exemption to vaccination.

The Covid-19 pandemic has lowered the vaccination rate with a worldwide coverage of 81%.

The measles vaccination rate in the United States usually is 95 to 97% nationwide and has dropped significantly with Covid-pandemic.

Remains a leading cause of vaccine preventable illnesses and deaths worldwide, that claims more than 100,000 lives each year.

It is estimated that measles vaccination has prevented an estimated 21.1 million deaths.

Universal vaccination resulted in the illumination of endemic measles in the US in the year 2000.

One of the most contagious directly transmitted pathogens, with outbreaks occurring in population in which fewer than 10% of their population are susceptible.

Outbreaks are initiated by international importation of measles by travelers who are mostly US residents, who acquired  measles in countries where the disease remains endemic and introduced into the communities upon their return.

Not a latent or persistent viral infection, and without animal reservoirs makes eradication possible.

Measles virus can be maintained only in humans by an unbroken chain of acute infections.

The virus is spread by airborne droplet nuclei, the dried residual of exhaled respiratory droplets, that can remain suspended in the air, and, the case of measles infectious  for up to two hours after infected person has left the area.

Susceptible patients exposed become contagious from the time they develop a prodrome  of fever followed by cough, coryza, and conjunctivitis preceding the rash for 2-four days, and remain contagious for 3-4 days after the rash appears.

Before universal vaccination all  children eventually develop measles as preschoolers or young school age children.

Maternal Immunity from the wild form of the virus provides passive immunity and protects  most infants until their second year of life.

An acute viral illness that starts with a prodromal phase and lasts 2-4 days, of fever and at least one of cough, coryza, and conjunctivitis, and similar to any upper respiratory tract infection.

In the pre vaccine era an average of 10,000 new cases of measles occured every day in the US.

Before the widespread vaccinations for measles, the virus caused 2-3,000,000 deaths globally per year.

Vaccination required for school attendance in every state.

In 2019, there has been a worldwide dramatic increase in infections due to non compliance receiving the MMR vaccine.

Transmission occurs among those who travel to areas where the virus persists, and occasional local transmission occurs.

Infants become susceptible to the virus when passively acquired maternal antibody is lost.

Exposed patients that are not immune have up to a 90% chance of contracting measles, and each person may go on to infect 9-18 other individuals, in a susceptible population.

Infants born to women with vaccine induced immunity are susceptible to measles at a younger age than those infants born to women with naturally acquired immunity.

The average age that people contract measles is related to the rate of decline of maternal bodies, the degree of contact with infected individuals, and the level of measles vaccine coverage in the population.

Endemic in most of the world but has been eliminated in the U.S. because of high rate of vaccination.

Children younger than five years, adults older than 20 years, pregnant women, and people with compromised immune system have the highest risk of measles complications which can include encephalitis and pneumonia.

Pneumonia is the most common cause of death for measles in young children.

In the US, one and five with measles who are unvaccinated require hospitalization

The most common side effects of the measles vaccine include a sore arm and fever.

About 5% of patients who receive the vaccine develop a rash, even the smaller number have a febrile seizure or transient decrease in platelet counts.

Very rarely meningocephalitis may occur as a result of the vaccine, almost always in immunocompromised patients.

Measles vaccination has prevented an estimated 21 million deaths worldwide since the year 2000.

Declared eliminated in 2000 in the US.

Most cases in the US are imported.

MMR vaccine recommended for routine use in all US children at age 12-15 months, with a booster at age 4-6 years.

Children aged 12 months or greater traveling internationally should receive 2 doses of MMR vaccine, separated by at least 28 days, aged 6-11 months should receive 1 dose of MMR vaccine.

One dose of vaccine prevents 93% of cases, while 2 doses prevent 97% of cases.

The degree of immunity can wane, but risk of infection is very low.

EEG changes reported in 50% of uncomplicated cases.

Diagnosis suggested by the presence of fever, maculopapular rash, cough, coryza, or conjunctivitis.

Diagnosis is a challenge during the prodromal phase because the rash may not be visible until 4-7 days after disease onset and how many patients with pre-existing immunity may have a modified pro longed incubation.

Rash develops in a cephalocaudal and centrifugal distribution.

The rash characteristically is erythematous macular papular exanthem appearing 2-4 days after the onset of fever, first on the face and head and then on the trunk and extremities.

The facial rash may be confluent on the face and upper body.

Cough, coryza, and conjunctivitis common.

Koplik ‘s spots are transient and seen in 50-70% of cases.

Headache, and GI symptoms are common.

CSF pleocytosis common.

Causes a variety of central nervous system syndromes, including meningitis, encephalitis, subacute sclerosing panencephalitis and acute disseminated encephalomyelitis.

Acute encephalitis develops in 35 to 100 of 100,000 measles patients.

Mortality rate of acute encephalitis is 10-20%, and neurologic damage occurs in 25% of survivors.

The basic reproduction number, that is, the number of secondary cases generated by one patient with measles ranges from 14 to 18.

The reproduction number is significantly higher than that for other airborne infectious diseases which are approximately 5-7.

Infants born to women with vaccine induced immunity are susceptible to measles at a younger age than those born to women with naturally acquired immunity.

Average age of contraction of measles depends on the rate of decline of protective maternal antibodies, the degree of contact with infected individuals, and the level of measles vaccine coverage.

90% of susceptible patients will develop measles who have close contact with a person with measles.

Viral transmission is by direct contact with infectious droplets by airborne spread.

Aerosolized droplet nuclei have been detected up to 2 hours after a measles patient has been in an area.

Patients with measles infectious 4 days before and after rash.

In urban settings with dense population and low vaccine coverage the disease affects mainly infants and young children.

With increasing measles vaccine coverage, and decreasing population density the age distribution for measles shifts to older children., adolescents and adulthood.

Mortality rate is increased in girls an estimated 5% over boys.

Patients who survive a measles infection remain vulnerable to other potentially deadly infections for as long as two or three years post-infection.

Complications occur in approximately 30% of cases.

Common complications include secondary infections related to induced immunosuppression, diarrhea, keratoconjunctivitis, otitis media, and pneumonia.

Pneumonia is the most common cause of measles related death.

Approximately one in 1000 cases of measles serious, even fatal, neurologic complications, such as encephalomyelitis, may occur.

Approximately one in 10,000 patients develop subacute sclerosing panencephalitist which can occur years after measles virus infection, with a severe, progressive, and fatal course.

The greatest risk of complications related to measles occurs in immuno suppressed individuals.

Immunosuppressed patients may have atypical presentations with severe complications.

Patients with significant immunosuppression cannot be safely vaccinated with the live-attenuated vaccine and must rely on heard immunity to protect them from measles infection.

Elevated liver functions care in 2/3 of patients in adult patients.

Tests such as a positive anti-measles virus IgM results or a four fold increase in levels of anti-measles virus IgG helpful in the diagnosis.

Detection of RNA measles virus by polymerase chain reaction allows genotype identification and helps distinguish wild type measles from vaccine associated measles during outbreaks.

Vaccine failure is divided into two categories: primary failure results from a lack of initial seroconversion, and secondary failure results from a loss of immunity after initial seroconversion.

Vaccination with 2 doses of measles-mumps -rubella vaccine recommended for children, with first dose at 12-15 months and second dose 4-6 years, before school entry.

Two doses of vaccine recommended for unvaccinated adults at exposure risk, and 1 dose for other adults 18 years or older.

Vaccine is alive, attenuated viral vaccine.

Measles vaccines contain M umps-rubella (MMR), and Measles-Mumps-rubella-varicella (MMRV) vaccine.

Standard and airborne precautions should be implemented, including isolating patients to negative pressure rooms.

No specific antiviral therapy is currently available.