Measles

Measles

DEFINITION
Measles is an acute highly contagious viral disease caused by measles virus. It is characterized by fever, cough, runny nose, red eyes and a generalized, maculopapular, erythematous rash. koplik’s spots .
The disease may complicated with brancho- pneumonia, encepholitis, hepatitis.
The lived attenuated measles virus vaccine has been utilized wildly since 1965.
Reservoir:Humans - no known animal reservoir.
The characteristic measles rash is classically described as a generalized, maculopapular, erythematous rash that begins several days after the fever starts. It starts on the head before spreading to cover most of the body, often causing itching. The rash is said to "stain", changing color from red to dark brown, before disappearing. The measles rash appears two to four days after initial symptoms, and lasts for up to eight days.
Is spread through respiration (contact with fluids from an infected person's nose and mouth, either directly or through aerosol transmission), and is highly contagious—90% of people without immunity sharing living space with an infected person will catch it. An asymptomatic incubation period occurs nine to twelve days from initial exposure and infectivity lasts from two to four days prior, until two to five days following the onset of the rash (i.e. four to 9 days infectivity in total).

ETIOLOGY

1 .Pathogen is measles virus.
It has been classed as a paramyxovirus.it is spherical in appearance ,measuring about 100~150nm in diameter.It has an outer envelope composed of M-protein, H-protein, F-protein, and internal core is RNA.
2 .Site of the measles virus exists
measles can be detected from blood and nasal, pharyngeal secretions.
3. Three kinds of antibodies are produced after infection,that is
3.1 complement combining antibody;
3.2 hemagglutinin inhibiting antibody
Neutralizing antibody
.Only one antigenic type of measles virus is known.
5. Resistance: measles virus is sensitive to heat or disinfectant , it is also inactivated by ultraviolet light easily.not strong


EPIDEMIOLOGY
1. Source of infection
The patients are the only source of infection.
2 .Routes of transmission
air-borne
3. Susceptibility of population
3.1 All age person is susceptible; 90% of contact people acquire the disease.
3.2 The permanent immunity acquire after disease.
4. Epidemic features
season:winter and spiring
age:6 months to 5 years old

Mortality in developed countries is ~1/1000. In sub-Saharan Africa, mortality is ~10%. In cases with complications, the rate may rise to 20–30%. On average, ~450 children die every day from measles.
Even in countries where vaccination has been introduced, rates may remain high. Globally, measles fell 60% from an estimated 873,000 deaths in 1999 to 345,000 in 2005. Estimates for 2008 indicate deaths fell further to 164,000 globally, with 77% of the remaining measles deaths in 2008 occurring within the Southeast Asian region.

Risk factors for measles virus infection include the following:

Children with immunodeficiency due to HIV or AIDS, leukemia, or corticosteroid therapy, regardless of immunization status
Travel to areas where measles is endemic or contact with travelers to endemic areas.
Infants who lose passive antibody before the age of routine immunization
Risk factors for severe measles and its complications include the following:
Malnutrition
Underlying immunodeficiency
Pregnancy
Vitamin A deficiency


The case fatality rate:
Between the years 1987 and 2000, the case fatality rate across the United States was three measles-attributable deaths per 1000 cases, or 0.3% . In underdeveloped nations with high rates of malnutrition and poor healthcare, fatality rates have been as high as 28%. In immunocompromised patients (e.g. people with AIDS) the fatality rate is approximately 30%.
CLINICAL MANIFESTATIONS
Typical type
1.Incubation period is approximately 6~18days,10days is the most common.
(3-4weeks)
2 .predromal phase: 3~4 days.
2 .1 Fever;
2 .2 Catarrhal inflammation of URT;
2 .3 Koplik’s spots;
2 .4 Transient prodromal rashes.
3. Eruption stage
3 .1. Time: the3~5 days after fever; but the 4th day is most common;
3 .2 . Shape: maculopapular
3.3. behind the ear→along the hairline→face→neck→chest→back→abdomen→limbs→hand and feet(palm,sole)
3 .4. The temperature rise continuously and companied with the toxic symptoms exaggerate
4 . Convalescent stage: Brown staining.Fine branny desquamation.
course:10-14 days
Atypical measles
1. Mild measles;
2. Severe measles (toxic and shock type measles);
3. hemorrhagic measles;
4. Variant measles.


COMPLICATIONS
1 .Bronchopneumonia;
2 .Myocarditis;
3 .Laryngitis;
4 .Neurologic complications:Encephalitis and SSPE .

LABORATORY FINDINGS
Blood routine
Serum Ab measurement
complement combining antibody;
hemagglutinin inhibiting antibody;
neutralizing antibody;
specific antibody IgM.
Other Ag and multinucleated giant cells
The separation of virus

DIAGNOSIS

1 .Epidemiologic data;
2 .Clinical manifestations;
3. Laboratory findings:
3 .1 .Multinucleated giant cells are detected in nasopharyax mucosa secretions;
.2 .Measles virus can be isolated in tissues culture;
3 .3 . Antibody titer;
3 .4 . WBC is relative low .


DIFFERENTIAL DIAGNOSIS
1 .Rubella (German measles) ;
2 .Rosella infantum
3. Drug rashes.

Treatment

.General therapy: rest, nursing and diet
2. Symptomatic therapy: fever and cough,
3.Support threapy:r-globulin
traditional Chinese herbs may be used ;
4. Treatment of complications

PREVENTION

1 .Control source of infection;
2 .Interruption of transmissions ;
3 .Protection of the susceptible person:
3.1. Active immunization
Lived attenuated measles vaccine.
Contraindications: pregnancy
3.2. Passive immunization
placenta globulin or gamma globulin.
<5 days prevent onset
>5 days relieve symptoms

In developed countries, most children are immunized against measles by the age of 18 months, generally as part of a three-part MMR vaccine (measles, mumps, and rubella). The vaccination is generally not given earlier than this because children younger than 18 months usually retain antimeasles immunoglobulins (antibodies) transmitted from the mother during pregnancy..


A second dose is usually given to children between the ages of four and five, to increase rates of immunity. Vaccination rates have been high enough to make measles relatively uncommon. Even a single case in a college dormitory or similar setting is often met with a local vaccination program, in case any of the people exposed are not already immune
In developing countries where measles is highly endemic, WHO doctors recommend two doses of vaccine be given at six and nine months of age. The vaccine should be given whether the child is HIV-infected or not The vaccine is less effective in HIV-infected infants, but the risk of adverse reactions is low.
Measles vaccination programs are often used to deliver other child health interventions, as well, such as bed nets to protect against malaria, antiparasite medicine and vitamin A supplements, and so contribute to the reduction of child deaths from other causes.
Measles Vaccine
Composition Live virus
Efficacy 95% (range, 90%-98%)
Duration of Immunity Lifelong
Schedule 2 doses

Methods of control:

1- Preventive measures:
a- Public education by health department and private physicians should encourage measles immunization for all susceptible.
b- Immunization
2- Control of patient, contact, and the immediate environment:
a- Report to local health authority.
b- Isolation: children should be kept out of school for 4 days after the appearance of the rash
c- Concurrent disinfection: not applicable
d- Quarantine : usually impractical, strict segregation of infant if measles occurs in institution.
e- immunization: of contacts : live virus vaccine should be
administered within 72 hr. of exposure ,and IG may be given for immunocompromised persons within 72 hr. for maximum protection
f- Investigation of contacts and source of infection
g- Specific treatment: None, during measles infection , Vit A supplementation, replace body reserve .
Saif AlDeen Adil Kamil