Lecture Notes: Acute Infections

Overview

• Types of Infections: Acute vs. Persistent
  • Acute Infections: Short-lived, either end in host's death or recovery.
  • Persistent Infections: Last a lifetime, will be covered in a future lecture.

Characteristics of Acute Infections

• Rapid Onset: Quick viral reproduction.
• Duration: Not necessarily short but limited.
• Severity: Can be severe, but not a defining trait.
• Immune Response: Often leads to immune clearance, though can also result in host death.
• Transmission: Efficient spread and high numbers of virus particles.

Inapparent Acute Infections

• Successful Infection Without Symptoms: Virus enters, reproduces, and spreads without causing disease symptoms.
• Detection via Serological Surveys: Presence of antibodies without recollection of symptoms.
  • Examples: Polio (90% inapparent), SARS-CoV-2 (20% inapparent).

Acute Viral Infections as Public Health Problems

• Rapid Spread: Often spread before symptoms arise.
• Asymptomatic Transmission: Significant in diseases like SARS-CoV-2.

Key Viruses Discussed

1. Influenza Virus

   • Types: A, B, C
   • Transmission: Respiratory droplets, direct contact.
   • Seasonality: Peaks in winter months.
   • Symptoms: Fever, cough, myalgia, can last weeks.
   • Complications: Pneumonia, myocarditis, Reye's syndrome.
   • Diagnostics: Rapid tests, clinical symptoms.

2. Measles Virus

   • Transmission: Highly contagious, respiratory droplets.
   • Pathogenesis: Starts in the respiratory tract, spreads via blood.
   • Symptoms: High fever, rash, Koplik spots.
   • Complications: Encephalitis, pneumonia, SSPE.
   • Vaccination: Highly effective in preventing outbreaks.

3. Polio Virus

   • Transmission: Fecal-oral route.
   • Pathogenesis: Viral reproduction in intestines, can lead to paralysis.
   • Symptoms: Often asymptomatic, paralysis in 1%.
   • Vaccination: Inactivated and oral vaccines available.

4. Norovirus

   • Symptoms: Gastroenteritis, vomiting, diarrhea.
   • Transmission: Fecal-oral, contaminated food/water.
   • Challenge Studies: Used to study transmission.
   • Outbreaks: Common in enclosed spaces like cruise ships and nursing homes.

5. West Nile Virus

   • Transmission: Mosquito-borne.
   • Symptoms: Often mild; can cause severe neurological disease.
   • Incidence: Higher in summer months.
   • Prevention: Mosquito control, personal protection.

General Prevention and Public Health Measures

• Hand Hygiene: Crucial for preventing norovirus.
• Vaccination: Key for controlling measles and influenza.
• Awareness: Understanding transmission routes to limit spread.

Next Lecture

• Topic: Persistent Infections
• Focus: Infections that do not resolve and persist in the host.