Untitled Quiz

West Nile Virus

• An acute systemic viral infection
  • It can cause mild, self-limited infections or neuroinvasive disease
  • The neuroinvasive disease is associated with long-term neurological sequelae
• The virus belongs to the Flaviviridae family, Genus Flavivirus
• It has a broad geographic distribution, including:
  • The Old World
  • Africa
  • The Middle East
  • Europe
• Diagnosis is mainly done through serology
• Other diagnostic methods include:
  • Viral culture
  • PCR

Epstein-Barr Virus

• Causes infectious mononucleosis
• It's a usually benign, self-limiting lymphoproliferative disorder
• Associated with various human tumors, including:
  • Lymphomas
  • Nasopharyngeal carcinoma
• Characterized by:
• Fever
• Sore throat
• Generalized lymphadenopathy
• Splenomegaly
• Appearance of mononucleosis cells in the blood
• Atypical activated T lymphocytes in the peripheral blood
• Certain individuals may also develop:
• Hepatitis
• Meningoencephalitis
• Pneumonitis
• Transmitted through close human contact
• Often spreads through saliva, especially during kissing, earning it the nickname "Kissing Disease"
• Usually occurs in late adolescents or young adults
• More common among upper socioeconomic classes in developed nations

Cytomegalovirus

• Commonly infects healthy young children and adults
• Usually asymptomatic
• About 50-100% of adults have CMV antibodies globally, indicating prior exposure
• The most common clinical manifestation:
• Infectious mononucleosis-like illness
  • Fever
  • Atypical lymphocytosis
  • Lymphadenopathy
  • Hepatitis
  • Marked hepatomegaly
  • Abnormal liver function tests
• CMV Mononucleosis:
• Affects children and adults
• Almost always symptom-free
• Infants with CMV or transplacental CMV infection:
• Might experience permanent deficits, such as:
  • Intellectual disability
  • Hearing loss
  • Neurologic impairments
• May develop congenital infections, including:
  • Interstitial pneumonitis
  • Hepatitis
  • Neurologic disorders
• Perinatal Infections:
  • Transmitted through the birth canal or breast milk
  • Usually asymptomatic due to protective maternal antibodies
  • Many individuals secrete CMV in urine and saliva for months or years
• Less common complications:
• Interstitial pneumonitis
• Failure to thrive
• Rash
• Hepatitis

Dengue Virus

• Transmitted by Aedes aegypti mosquitos
• Clinical manifestations range from mild to severe:
  • Fever with headache
  • Macular rash
  • Severe myalgias (breakbone fever)
  • Severe dengue (Dengue hemorrhagic fever):
  • Bleeding
  • Liver failure
  • Reduced consciousness
  • Organ failure
  • Plasma leakage
• Severe dengue leads to shock and respiratory distress
• Widespread hemorrhages throughout the body with:
  • Hepatic necrosis
  • Mononuclear infiltrates
  • Septal thickening
  • Hyaline membrane formation in the lung
• The immune response to dengue virus dictates the severity of infection
• Dengue virus has four serotypes:
• Each serotype infection provides protective immunity to that specific serotype
• Mechanism of increasing vascular permeability in severe dengue:
• Not fully understood
• Evidence suggests reactive oxygen species, enzymes, and proinflammatory molecules breakdown the glycocalyx layer
• Allows plasma to reach intercellular junctions and leak out into the tissues
• The blood vessel wall integrity is altered

Histologic Analysis of Lung Tissue in Dengue

• Diffuse Alveolar Damage (DAD) is observed:
  • Previously known as acute respiratory distress (ARDS)
  • Characterized by alveolar collapse
  • Some alveoli are collapsed, while others are distended
  • Lined by a hyaline membrane
  • Dense, thick, pink bands of proteinaceous material
  • Accompanied by inflammation
  • Inflammatory infiltrates consist mainly of mononuclear cells, similar to dengue (macrophages and lymphocytes)

Pathology of Viral Infections

• Comparison of lymphoid tissues
• Normal lymphoid tissues:
• Paracortical area (dark purple area surrounding the germinal center)
• Expansion is due to T cell activation (immunoblasts)
• Hyperplastic lymphoid tissues:
• Shows an expansion of white pulp follicles (paracortical area) and red pulp sinusoids
• Vulnerable to rupture
• T cell proliferation may be exuberant
• Makes it difficult to differentiate nodal morphology
• Follicles (B cell area) might exhibit mild hyperplasia

Liver Pathology

• The liver is usually involved to some extent
• Moderate hepatomegaly
• Histology:
  • Atypical lymphocytes in portal areas and sinusoids
  • Scattered isolated cells or foci of parenchymal necrosis

Spleen Pathology

• Enlarged spleen
• The organ often shows:
  • Expansion of white pulp follicles
  • Expansion of red pulp sinusoids
  • Vulnerable to rupture

Centrocytes vs. Other Cells

• Centrocytes:
  • Small, cleaved cells with a cleft nucleus
  • Nucleus is centrally located
• Centroblasts:
  • Larger cells with a nucleus located at the periphery
  • Open chromatin
  • Several nucleoli
  • Modest amount of cytoplasm