Introduction to Microbiology Anas Abu-Humaidan M.D. Ph.D. Lecture 28

Viruses overview The following diseases associated with childhood exanthems (طفح) will be discussed in this lecture: mumps, measles, rubella, erythema infectiosum roseola The name “first,second, third, etc… disease" comes from its place on the standard list of rash-causing childhood diseases, which includes: Measles (first), scarlet fever (second), rubella (third), Dukes' disease (fourth, but is no longer widely accepted as distinct), erythema infectiosum (fifth) and roseola (sixth).

Mumps virus A paramyxovirus. Enveloped, negative sense single-stranded RNA virus with hemagglutinating and neuraminidase activity. Initiates infection by attachment of the HN spike to sialic acid on the cell surface It replicates in the cytoplasm by using its own RNA-dependent RNA polymerase, and the progeny viruses are released by budding from the cell membranes.

Mumps / النكاف / ابو دغيم High infectivity is present before and after onset of illness High frequency in 5-15 years age group Person-to-person transmission via respiratory route

Mumps virus Mumps virus can be readily isolated early in the illness from the saliva, pharynx, and other affected sites, such as the cerebrospinal fluid (CSF) Since 1967, a live attenuated vaccine that is safe and highly effective has been available.

Measels virus A Paramyxovirus. Enveloped, negative-sense, single-stranded RNA virus has hemagglutinin and fusion glycoproteins. CD46 is a cell receptor

Measels/ الحصبة Figure 10–5. Measles rash on day 4 of illness. Common synonyms for measles include rubeola, 5-day measles, and hard measles Bacterial superinfection (otitis, pneumonia, sepsis) is the most common complication Figure 10–4. Oral Koplik spots on day 3 of measles

Measels/ الحصبة Live attenuated measles vaccine is available and highly immunogenic, and is most commonly administered as MMRV the vaccine should be administered to infants at 12 to 15 months of age with a second dose at 4 to 6 or 11 to 12 years of age.

Rubella virus Enveloped togavirus (rubivirus) contains single-stranded (+) RNA Viral spikes E1 and E2; E1 binds to receptor and is involved in virus neutralization

Rubella الحصبة الالمانية Figure 10–8. Rubella rash. Diffuse, macular in appearance Rubella virus has high infectivity but low virulence. Only 30% to 60% of rubella-infected susceptible persons develop clinically apparent disease Childbearing women are the major concern. Spread to the fetus leads to a chronic infection and congenital abnormalities.

Rubella الحصبة الالمانية Rubella is commonly known as German measles or 3-day measles A live attenuated rubella vaccine has been available for routine immunization either alone or in combination (MMRV).

PARVOVIRUS B19 Small naked, single-stranded DNA viruses. A primary site of replication appears to be the nucleus of an immature cell in the erythrocyte lineage that is mitotically active. infected cells then cease to proliferate. This is only a problem in immunocompromised patients or patients with hemolytic anemia. Parvovirus B19 causes disease in humans (children) known as erythema infectiosum, slapped face, or fifth disease.

Erythema infectiosum After an incubation period of 4 to 12 days, a mild illness appears, characterized by fever, malaise, headache, myalgia, and itching in varying degrees. Like rubella, active transplacental transmission of parvovirus B19 can occur during primary infections in the first 20 weeks of pregnancy, sometimes resulting in stillbirth of fetuses that are profoundly anemic. No vaccine currently available.

Roseola infantum Is a common illness observed in infants and children 6 months to 4 years of age. Associated with human herpesvirus type 6 or type 7. The illness is characterized by abrupt onset of high fever, sometimes accompanied by brief, generalized convulsions and leukopenia. After 3 to 5 days, the fever diminishes rapidly, followed in a few hours by a faint, transient, macular rash.

Viruses overview The following diseases associated with childhood exanthems (طفح) will be discussed in this lecture: mumps, measles, rubella, erythema infectiosum roseola The name “first,second, third, etc… disease" comes from its place on the standard list of rash-causing childhood diseases, which includes: Measles (first), scarlet fever (second), rubella (third), Dukes' disease (fourth, but is no longer widely accepted as distinct), erythema infectiosum (fifth) and roseola (sixth).

Viruses overview

Viruses overview

Viruses overview

Further reading: Sherris Medical Microbiology, sixth edition Chapter 10,11