infectious disease

Infectious disease 2

Dr. Athal Humo
ROSEOLA INFANTUMEXANTHEM SUBITUMSixth disease ( common )
مهمة جدا
Epidemiology
Transplacental antibody protects most infants until 6 months of age. The incidence of infection increases as maternally derived antibody levels decline. By 2 to 3 years of age, approximately all children are seropositive for viral antibody.
Virus is likely acquired from asymptomatic adults who periodically shed these viruses.
It is caused primarily by human herpes virus type 6 (HHV-6), and by HHV-7 in 10% to 30% of cases. HHV-6 and HHV-7 are DNA viruses, which are of the herpesvirus family.
HHV-6 is a major cause of acute febrile illnesses in infants and may be responsible for 20% of visits to the emergency department for children 6 to 18 months old.

Clinical Manifestations

Roseola is characterized by high fever (often ≥40°C which may be accompanied by fussiness) lasting 3 to 5 days.
Followed by maculopapular, rose-colored rash that appears with the remission of fever, although it may present earlier. The rash usually lasts 1 to 3 days but may fade rapidly & is not present in all infant.
Roseola is associated with approximately one third of febrile seizures.
Roseola caused by HHV-6 and HHV-7 is clinically indistinguishable, although HHV-6 associated roseola typically occurs in younger infants.
LABORATORY FINDINGS
The most characteristic laboratory findings noted are lower mean numbers of total WBC, lymphocytes, and neutrophils counts.
Encephalitis with roseola is characterized by:
Minimal CSF pleocytosis with mild elevations of protein and normal glucose concentration.
Serologic testing showing a fourfold rise in acute and convalescent sera.
Documentation of HHV-6 DNA by PCR in the CSF is diagnostic.
Treatment
There is no specific therapy for roseola. Routine supportive care includes maintaining adequate hydration and antipyretics.
In immunocompromised hosts, use of ganciclovir or foscarnet can be considered


ERYTHEMA INFECTIOSUM FIFTH DISEASE
Epidemiology
caused by the human parvovirus B19
Single stranded DNA virus.
Benign self-limited illness affecting any age mostly 5-15 yrs old and even adults .
Seasonal peaks occur in the late winter and spring, with sporadic infections throughout the year.
Incubation period average 15-17 days .It is transmitted by respiratory secretions airborne route & also transmissible in blood and blood products
it an important cause of aplastic crisis in patients with hemolytic anemias like thalassemia, sickle anemia & spherocytosis. Parvovirus B19 also causes severe fetal anemia and even hydrops fetalis after primary infection during pregnancy
Clinical Manifestations
Parvovirus B19 infections usually begin with a mild prodromal nonspecific illness characterized by low grade fever, malaise, myalgias, and headache.
This illness is followed by the characteristic rash within few days (Erythema Infectiosum) , which occurs in 3 stages that are not always distinguishable.
Stage 1: erythematous cheeks, appearing as a "slapped cheek" rash with circumoral pallor. The exanthem may appear like a sunburn, occasionally is edematous.
Stage 2: an erythematous symmetric, maculopapular rash appears 1 to 4 days later, spreading on trunk & proximal extremities (rash tends to be more prominent on extensor surfaces, sparing the palms and soles) then fades as central clearing takes place, giving a distinctive lacy reticulated rash that lasts 2 to 40 days (mean 11 days). This rash may be pruritic & does not desquamate.
Stage 3: the rash wax and wane over 1-3 wk on exposure to sunlight, heat, exercise, bathing, rubbing and stress.
Other features of the rash are as follows:
The rash is often pruritic, especially in adults.
Enanthems are virtually never observed.
The patient is no longer infectious when the rash appears
Arthropathy: joint symptoms are much more common among adults and older adolescents with B19 infection.
Transient Aplastic Crisis: occurs in patients with all types of chronic hemolysis characterized by ineffective erythroid production typically lasting 7 to 10 days. patients with aplastic crisis are ill with fever, malaise, and lethargy and have signs and symptoms of profound anemia, including pallor, tachycardia, and tachypnea. Rash is rarely present. The reticulocyte count is extremely low, and the hemoglobin level is lower than usual for the patient. Transient neutropenia and thrombocytopenia also commonly occur.
Immunocompromised Persons: chronic anemia is the most common manifestation, sometimes accompanied by neutropenia, thrombocytopenia, or complete marrow suppression.
Fetal Infection: primary maternal infection is associated with nonimmune fetal hydrops and intrauterine fetal demise.
Laboratory Studies
Hematologic abnormalities occur with parvovirus infection, including reticulocytopenia lasting 7 to 10 days, mild anemia, thrombocytopenia, lymphopenia, and neutropenia.


Detection of Parvovirus B19 by
PCR
Electron microscopy of erythroid precursors in the bone marrow.

Serologic tests showing specific IgM antibody to parvovirus are diagnostic, demonstrating infection that probably occurred in the prior 2 to 4 months.
Treatment
There is no specific therapy for roseola. Routine supportive care includes maintaining adequate hydration and antipyretics.
In immunocompromised hosts, use of ganciclovir or foscarnet can be considered

VARICELLA-ZOSTER VIRUS INFECTION

Chickenpox (varicella) جدا جدا مهمة ( قراءة كاملة )
DNA virus that is a member of the herpesvirus family
Humans are the only natural host.
VZV (chickenpox) is highly communicable among susceptible individuals.
It is mild disease in young children but may be severe in adult and in immunocompromised children.
The period of infectivity to others; ranges from 2 days before to 7 days after the onset of the rash till when all lesions are crusted and dried.
Epidemiology
In the prevaccine era, the peak age of occurrence was 5 to 10 years.
In the postvaccine era, the incidence of varicella has declined in all age groups, with the peak incidence now in 10 to 14 year olds.
Peak seasonal infection in late winter and spring.
Transmission is by direct contact, droplet, and air.
Clinical Manifestations
The incubation period of varicella is generally 14 to 16 days.
Prodromal symptoms of fever, malaise, and anorexia, running nose may precede the rash by 1 day.
The characteristic rash appears initially as small red papules that rapidly progress to oval, "teardrop" vesicles on an erythematous base. The fluid progresses from clear to cloudy, and the vesicles ulcerate, crusted, and dried and heal. New crops appear in 3 to 4 days, usually beginning on the trunk followed by the head, the face, and, less commonly the extremities, with all stages of lesions being present at the same time(crop). Pruritus is universal.
Lesions may be present on mucous membranes.
Lymphadenopathy may be generalized.
The severity of the rash varies, as do systemic signs and fever, which generally abate after 3 to 4 days.
Laboratory Studies
Laboratory testing confirmation for diagnosis is usually unnecessary.
PCR is the current diagnostic method of choice, and genotyping to distinguish vaccine and wild-type strains is available through the CDC.
Detection of varicella-specific antigen in vesicular fluid by immunofluorescence using monoclonal antibodies or demonstration of a fourfold antibody increase of acute and convalescent sera is also diagnostic but not as sensitive as PCR.
Treatment
Symptomatic therapy of varicella includes nonaspirin antipyretics, cool baths, and careful hygiene.
Routine oral administration of acyclovir is not recommended in otherwise healthy children with varicella.
Indication of antiviral (acyclovir) therapy:
Early therapy with antivirals (especially within 24 hours of rash onset) in immunocompromised persons is effective in preventing severe complications, including pneumonia, encephalitis, and death from varicella.
Acyclovir or valacyclovir may be considered in those at risk of severe varicella, such as:
unvaccinated persons older than 12 years.
those with chronic cutaneous or pulmonary disease.
receiving short course, intermittent, or aerosolized corticosteroids.
receiving long-term salicylate therapy.
Complications
Varicella is a more severe disease for neonates, adults, and immunocompromised persons.
Secondary infection of skin lesions by streptococci or staphylococci is the most common complication. Hemorrhagic lesions may occur, known as varicella gangrenosa .
Pneumonia is uncommon in healthy children but occurs more in healthy adults and immunocompromised persons.
Myocarditis, pericarditis, orchitis, hepatitis, ulcerative gastritis, glomerulonephritis, and arthritis may complicate varicella.
Reye syndrome may follow varicella; thus, salicylate use is contraindicated during varicella infection.
Neurologic complications frequently include postinfectious encephalitis, cerebellar ataxia & Guillain-Barre syndrome.
Prevention
Children with chickenpox should not return to school until all vesicles have crusted.
A hospitalized child with chickenpox should be isolated to prevent transmission.
A live attenuated varicella vaccine—two doses for all children— is recommended. The first dose should be administered at age 12 to 15 months and the second dose at 4 to 6 years.
Varicella vaccine is 85% effective in preventing any disease and 97% effective in preventing moderately severe and severe disease.
Passive immunity can be provided by VZIG, which is indicated within 4 days of exposure for susceptible individuals at increased risk for severe illness. It is recommended for:
immunocompromised children
pregnant women
newborns exposed to varicella.
Hospitalized premature infants born at ≥28 weeks of gestation whose mothers do not have evidence of immunity to varicella.
Hospitalized premature infants born at <28 weeks of gestation or who weigh ≤1,000 g at birth, regardless of their mothers' evidence of immunity to varicella.
≥15 yr and older, who are exposed to infection.


Zoster (shingles)
( Rere in children )
It is the manifestation of reactivated latent infection of endogenous VZV.
Zoster is transmitted by direct contact.
Only 5% of cases of zoster occur in children younger than 15 years of age, with 75% of cases occurring after 45 years of age. The incidence of zoster is increased in immunocompromised persons.
Clinical Manifestations
The preeruption phase of zoster includes intense localized and constant pain and tenderness (acute neuritis) along a dermatome, accompanied by malaise and fever.
In several days, the eruption of papules, which quickly vesiculate, occurs in the dermatome or in two adjacent dermatomes. Groups of lesions occur for 1 to 7 days and then progress to crusting and healing.
Thoracic and lumbar regions are typically involved.
Lesions generally are unilateral and are accompanied by regional lymphadenopathy.

Any branch of cranial nerve V may be involved, which also may cause corneal and intraoral lesions. Involvement of cranial nerve VII may result in facial paralysis and ear canal vesicles (Ramsay Hunt syndrome). Ophthalmic zoster may be associated with ipsilateral cerebral angiitis and stroke.
Immunocompromised persons may have unusually severe, painful herpes zoster that involves cutaneous and, rarely, visceral dissemination (to liver, lungs, and central nervous system).
Postherpetic neuralgia, defined as pain persisting longer than 1 month, is uncommon in children.
Treatment
Antiviral treatment of zoster accelerates cutaneous healing, hastens the resolution of acute neuritis, and reduces the risk of postherpetic neuralgia.
Acyclovir is recommended for children.
congenital varicella
Fetal varicella during first 6 months of pregnancy includes followings pathological effects: low birth wt, cortical brain atrophy, mental retardation, cataract, microcephaly, cicatrical scarring of body and limbs with aplasia of fingers and toes .