Viral Diseases Affecting the Human Respiratory and Integumentary Systems

Mumps

Overview and Transmission

Mumps is a self-limited viral illness primarily affecting the salivary glands, leading to painful swelling. It is caused by the mumps virus and is transmitted via airborne droplets.

• Reservoir: Humans are the only known reservoir.

• Subclinical Infections: Approximately 40% of infections are subclinical, but infection confers long-term immunity.

• Incidence: About 3,000 cases per year in the U.S.

Clinical Manifestations and Complications

• Symptoms: Fever, muscle pain, malaise, and swelling of one or both cheeks due to parotid gland involvement.

• Complications: In 20–30% of infected adult males, the testes may become infected (orchitis); sterility is rare.

Treatment and Prevention

• Treatment: Symptomatic management.

• Prevention: Live attenuated MMR vaccine (Measles, Mumps, Rubella).

Measles (Rubeola)

Etiology and Transmission

Measles is caused by the Morbillivirus and is highly contagious, transmitted by respiratory aerosols. It is distinct from German measles (rubella).

• Reservoir: Humans only.

• Incidence: Less than 100 cases/year in the U.S.; a frequent cause of death worldwide.

Pathogenesis and Symptoms

• Initial Infection: Virus invades the mucosal lining of the respiratory tract.

• Symptoms: Sore throat, dry cough, headache, conjunctivitis, lymphadenitis, fever.

• Koplik's Spots: Characteristic oral lesions.

• Exanthem: Rash eruption starting on the head, progressing to trunk and extremities.

Complications

• Neurological Degeneration: Rarely, progressive degeneration of the cerebral cortex, white matter, and brain stem (1 case per million infections).

• Pathology: Defective virus spreads through the brain by cell fusion, leading to coma and death in months or years.

Prevention

• Vaccine: Live attenuated MMR vaccine.

Rubella (German Measles)

Etiology and Transmission

Rubella is caused by Rubivirus, a Togavirus with single-stranded RNA (ssRNA). It is an endemic disease, with most cases reported in adolescents and young adults.

• Transmission: Respiratory route.

Clinical Forms

• Postnatal Rubella: Malaise, fever, sore throat, lymphadenopathy, rash; generally mild and lasts about 3 days.

• Congenital Rubella: Infection during the first trimester can cause miscarriage or multiple defects (cardiac abnormalities, ocular lesions, deafness, mental and physical retardation).

Treatment and Prevention

• Treatment: No specific treatment available; diagnosis based on serological testing.

• Prevention: Live attenuated MMR vaccine.

Varicella-Zoster Virus (VZV)

Etiology and Transmission

VZV is a double-stranded DNA herpesvirus, with humans as the only natural host. Transmission occurs via respiratory droplets and direct contact.

• Primary Infection: Chickenpox, characterized by vesicular skin lesions.

• Latency: Virus enters neurons and remains latent.

• Reactivation: Causes zoster (shingles), more common in older patients and follows dermatomal distribution.

Diagnosis

• Clinical Recognition: Cutaneous manifestations are characteristic.

• Laboratory Confirmation: Multinucleate giant cells in vesicle scrapings; fluorescent antibody detection, DNA typing, or culture.

Treatment and Prevention

• Treatment: Antiviral drugs (e.g., acyclovir, famciclovir).

• Prevention: Live attenuated vaccine (Varivax) for chickenpox and shingles.

The Common Cold

Etiology and Transmission

The common cold is the most frequent infectious disease, caused by various viruses and transmitted via airborne droplets, direct contact, and fomites.

• Major Pathogens: Rhinoviruses, Coronaviruses, Adenoviruses, Coxsackie viruses, Respiratory Syncytial Virus (RSV), Orthomyxoviruses.

• Incidence: Infections are usually of short duration and milder than other respiratory diseases.

Symptoms and Immunity

• Symptoms: Rhinitis, nasal obstruction, watery nasal discharges, malaise, headache, chill, fatigue, sore throat, cough.

• Immunity: Each infection induces specific immunity, but the diversity of pathogens prevents complete protection or effective vaccines.

Treatment and Prevention

• Treatment: Symptomatic management with antihistamines and decongestants; most antiviral drugs are ineffective.

• Prevention: Handwashing and careful handling of nasal secretions.

Coronaviruses

Overview and Transmission

Coronaviruses are relatively large RNA viruses with distinctively spaced spikes on their envelopes. They are common in domesticated animals and humans.

• Human Types: Seven types identified; four cause mild upper respiratory infections.

• Transmission: Aerosol, droplet, and direct contact.

Severe Acute Respiratory Syndrome (SARS)

• Symptoms: Fever, chills, headache, body ache, diarrhea, sore throat, shortness of breath, acute respiratory distress, and pneumonia.

• Diagnosis: Detection of antibodies or amplification of viral RNA.

• Treatment: Supportive care.

Adenoviruses

Overview and Transmission

Adenoviruses are nonenveloped, double-stranded DNA viruses. Thirty types are associated with human disease, though oncogenicity is seen only in animals.

• Transmission: Respiratory and ocular secretions.

Bordetella pertussis (Whooping Cough)

Etiology and Transmission

Bordetella pertussis is a Gram-negative, aerobic coccobacillus causing pertussis (whooping cough), an acute respiratory syndrome most severe in infants.

• Reservoir: Apparently healthy carriers.

• Transmission: Airborne or direct contact.

Pathogenesis and Symptoms

• Pathogenesis: Toxins destroy and dislodge ciliated epithelial cells, leading to mucus buildup and airway blockage.

• Symptoms: Severe coughing fits (whooping cough), which can be life-threatening in babies.

Prevention

• Vaccine: DTaP (Diphtheria, Tetanus, acellular Pertussis).