what is measles:-

MEASLES

Microbiology

what is measles:-

Measles is a single-stranded RNA paramyxovirus with one

antigenic type. Humans are the only reservoir. Measles

virus infects the upper respiratory tract and regional lymph

nodes and is spread systemically during a brief, low-titer

primary viremia. It is more prevalent in winter and spring.

A secondary viremia occurs within 5–7 days when virus infected

monocytes spread the virus to the respiratory tract,

skin, and other organs. The characteristic histological  finding

is the presence of large, multinucleated giant cells (Warthin-

Finkeldey cells) and syncytium formation in respiratory

epithelia and reticulo-endothelial cells. Virus is present

in respiratory secretions, blood, and urine of infected

individuals. Measles virus is transmitted by large droplets

from the upper respiratory tract and requires close contact.

Incubation Period

Eight to twelve days from exposure to the onset of symptoms

Infective Period

Period of infectivity is from 1 to 2 days before symptoms (about

5 days before onset of rash) to 4 days after the appearance of

the rash.

Mode of Transmission

Measles is highly contagious. Measles virus is typically

transmitted by respiratory droplets, direct contact, or vomits

Infants less than one year rarely acquire measles due to passage

of maternal antibodies.

Clinical Features

*Stages of Infection

Classic measles infection can be subdivided into the following

clinical stages: prodromal, eruptive, and convalescent.

1-Prodromal: The prodromal  usually lasts for 2–3 days but may

persist for as long as 8 days

The prodromal  phase is defined by the appearance of

symptoms which typically include fever, malaise, and anorexia,

followed by conjunctivitis, coryza, and cough. The severity of

conjunctivitis is variable and may also be accompanied by

lacrimation or photophobia. The respiratory symptoms are due

to mucosal inflammation from viral infection of epithelial cells.

Fever is typically present; the pattern may be variable. Various

fever patterns have been described; fever as high as 40oC can

occur.

Koplik’s spot: Patients may develop an enanthem known as

Koplik’s spots; Koplik’s spots (Fig. 2) in patients with suspected

measles, are considered pathognomonic for measles infection

and occur approximately 48 hours before the characteristic exanthem appears.These are 1 to 3 mm whitish, grayish,

or bluish elevations with an erythematous base, typically seen

on the buccal mucosa opposite the molar teeth, though they

can spread to cover the buccal and labial mucosa as well as the

hard and soft palate. They have also been described as “grains

of salt on a red background”. Koplik’s spots subsequently may

coalesce and generally last 12 to 72 hours.

2-Eruptive phase: Starts on 4–5th day of illness when fever

rises again. The exanthem of measles is a maculopapular

, blanching rash beginning on the face and spreading

cephalocaudally and centrifugally to involve the neck, upper

trunk, lower trunk, and extremities. The lesions may become

confl uent, especially in areas such as the face, where the rash

develops first. The rash may also have some petechiae; in severe

cases, it may appear hemorrhagic. In general, the extent and

degree of confluence of the rash correlates with the severity of

the illness in children. The palms and soles are rarely involved.

The cranial to caudal progression of the rash is characteristic

of measles but is not pathognomonic.

Other characteristic findings during the exanthematous

phase include lymphadenopathy, high fever (peaking two to

three days after appearance of rash), pronounced respiratory

signs including pharyngitis, and nonpurulent conjunctivitis.

Koplik’s spots often begin to slough when the exanthem

appears.

Clinical improvement typically ensues within 48 hours of

the appearance of the rash. After three to four days, the rash

darkens to a brownish color and begins to fade, followed by

fine desquamation. The rash usually lasts six to seven days.

Hyperpigmented skin lesion may persist long after active

measles infection, and is an evidence of post-measles infection.

Hyperpigmented skin lesion may persist long after active measles infection and an evidence of post-measles infection

3-Convalescent phase: Cough may persist for one to two weeks

after measles infection. The occurrence of fever beyond the

third to fourth day of rash suggests a measles-associated

complication. Immunity after measles infection is thought to be

lifelong, although there are rare reports of measles re-infection.

Diagnosis

Mostly clinical depending upon history and clinical examination.

Koplik’s spot seen is pathognomonic. Post-measles desquamation

and hyperpigmentation are too characteristics. Cases of modified

measles and atypical measles could be confusing when measles

specifi c antibody in paired sera is useful.

Differential Diagnosis

• Other exanthematous immune-mediated illnesses and

infections,

– Rubella (rash is similar but prodrome is milder,

there is a prominent retroauricular or suboccipital

lymphadenopathy)

– Adenoviruses

– Enteroviruses

– Epstein-Barr virus (characterized by sore throat,

lymphadenopathy and splenomegaly)

• Exanthem subitum or Roseola infantum rash usually

appears after disappearance of fever and erythema

infectiosum (in older children)

• Mycoplasma pneumoniae and group A Streptococcus may

also produce rashes similar to measles

• Kawasaki syndrome: It can manifest many of the same

findings as measles but lacks discrete intraoral lesions

(Koplik’s spots) and a severe prodromal cough. Typically

has elevated neutrophils and acute-phase reactant levels.

In addition, the characteristic thrombocytosis of Kawasaki

syndrome is absent in measles

• Drug eruptions (history of specific drug consumption).

Laboratory Investigations

• Complete blood count (CBC)

Leukopenia, T-cell cytopenia, and thrombocytopenia may

be observed during measles infection

• Chest radiography may demonstrate interstitial

pneumonitis

• Biopsy samples of lymphoid tissues before the appearance

of the exanthem may demonstrate reticuloendothelial

giant cells.

• Histologic analysis of  enanthem or exanthem and cytologic

examination of nasal secretions may also demonstrate

epithelial giant cells.

Treatment

Mainly symptomatic and supportive with nutritional support

• Maintenance of hydration, oxygenation, and comfort are

goals of therapy

• Antipyretics for comfort and fever control

• For patients with respiratory tract involvement, airway

humidification and supplemental oxygen

• Ventilatory support may be required for respiratory failure

due to croup or pneumonia

• Antiviral therapy is not effective in otherwise normal

healthy patients

• Antibiotics are indicated in superadded bacterial infection

in the convalescent phase.

Vitamin A in Measles

Vitamin A can reduce the severity and complications of

measles. Published studies revealed that measles associated

death increases about 24% in vitamin A deficient children.

Dose of Vitamin A

200,000 1U orally for children ≥1 year of age and 100,000 IU for

children 6 months to 1 year of age, two doses on D1 and D2.

Patients suffering from measles should be off ered protein

and energy-dense diet and increment of two additional daily

diets at least for 6 weeks to prevent subsequent malnutrition.

Complications

Case fatality from complications of measles, in developing

countries is 4–6%. Risk groups for developing complications are:

• Immuno-compromised hosts

• Pregnant women

• Individuals with vitamin A deficiency or poor nutritional

status

• Individuals at the extremes of age.

Measles causes disseminated infection, so multiple systems

and organs are affected.

• Pulmonary: Respiratory tract infections (most frequently

occurs among patients <5 years and >20 years)

– Interstitial pneumonia

– Post-measles bronchopneumonia due to Streptococcus

pneumoniae, Streptococcus pyogenes, Haemophilus

infl uenzae, and Staphylococcus aureus

– Laryngotracheobronchitis (croup both pre-eruptive

croup and posteruptive croup)

– Otitis media occurs in 5 to 10 percent of cases

– Bronchiectasis

– Flaring up of latent tuberculosis

– Coinfection with other viruses like parainfl uenza and

adenovirus.

• Neurologic

– Febrile seizure

– Encephalitis: Usually appears within a few days of

the rash. It is associated with a CSF pleocytosis (predominantly

lymphocytes), increased protein levels,

and normal glucose

– Acute disseminated encephalomyelitis: Acute

disseminated encephalomyelitis (ADEM) is a demyelinating

disease that presents during the recovery phase

of measles infection, typically within two weeks of the

exanthem. ADEM is also known as postinfectious or

postvaccination encephalomyelitis

– The major manifestations of ADEM include fever,

headache, neck stiff ness, seizures, and mental status

changes such as confusion, somnolence, or coma.

Other findings may include ataxia, myoclonus,

choreoathetosis, and signs of myelitis, such as

paraplegia, quadriplegia, sensory loss, loss of bladder

and bowel control, and, in patients with myelitis,

back pain. Analysis of cerebrospinal fl uid generally

demonstrates a lymphocytic pleocytosis and elevated

protein concentration

– Subacute sclerosing panencephalitis

– Subacute sclerosing panencephalitis (SSPE) is a fatal,

progressive degenerative disease of the central nervous

system that occurs 7 to 10 years after natural measles

infection

– Others

Other neurologic complications associated with measles

include acute measles-induced encephalopathy

• Malnutrition

Measles is a common antecedent of malnutrition (Fig.

4), lasting for 2–4 weeks in healthy children and it can

also increase the severity of malnutrition and can make

previously existing nonsevere malnutrition to severe acute

malnutrition (SAM), a potentially serious condition with

high-case fatality.

• Eye manifestations

– Measles-induced keratitis (a common cause of

blindness)

– Corneal ulceration

• Gastrointestinal

– Gingivostomatitis

– Diarrhea

– Gastroenteritis

– Hepatitis

– Mesenteric lymphadenitis

– Appendicitis.

In developing countries, measles-induced stomatitis and

diarrhea can lead to worsening of nutritional status.

• Cardiac

Cardiac complications of measles include myocarditis and

pericarditis

• Immunosuppression: Measles infection can lead to

systemic immune suppression and severe secondary

infections, especially in the developing world. These

eff ects are caused by direct infection of T cells by measles

virus and by infection of dendritic cells, impairing their

important antigen presenting/accessory function in T cell

activation.

Due to immunosuppressant properties, children

suffering from bronchial asthma may get temporary

relief of breathing difficulty as it behaves like steroid.

However its adverse effects in such cases far outweigh its

bronchodilator property. Similarly, children with nephritic syndrome with measles may develop brisk diuresis as it also

works here as steroid (immunosuppressant).

Prevention

• Isolate the patient during its infective period

• Measles vaccine given within 72 hours of exposure can

prevent measles in contact as incubation period of vaccine

measles virus is less than natural measles virus and

produces immunity earlier than natural measles virus, due

to earlier subclinical infection of attenuated vaccine virus.

Measles Vaccine

With the absence of an intermediary host, measles vaccine

has generated a lot of interest for potential eradication. Hence

the measles vaccination has a lot of importance at the national

and international level. Maternal antibody provides protection

for first 6 to 9 months of infancy. A number of live attenuated

vaccines are available against measles either as monovalent

measles vaccine or measles containing vaccine (MCV). The

MCV are MMR (measles, mumps and rubella), MMRV (measles,

mumps, rubella, and varicella) and MR (measles and rubella).

Two doses of measles vaccine are given. Th e fi rst dose is

given with MR (measles and rubella) in EPI schedule. The

second dose is given at 15th month as monovalent measles

vaccine according to EPI schedule. However instead of

monovalent measles vaccine given by EPI, measles vaccine

containing combination vaccine MMR (measles, mumps, and

rubella) can be given at 15th month.

In areas with high measles transmission, the first dose of

MCV (MR, MMR) should be administered at nine month. All

unvaccinated children over nine month should receive their

vaccine as soon as possible. In countries with low risk of measles

transmission, the first dose may be administered at 12 months.

The optimum timing for second dose is 15 to 18 months.

Measles vaccines are safe, effective, inexpensive and

provide long lasting immunity. Hence all countries should aim

at providing two doses of vaccine.