Infections Respiratoires Émergentes: Grippe et Covid-19

Infections Respiratoires Émergentes : Grippe et Covid-19

• Introduction - Généralités: Acute viral illness, highly contagious, transmitted via airborne droplets. Typically mild in healthy young adults, but can lead to serious complications in older adults and those with chronic conditions.

• Annual global figures: Average of approximately 3 million severe cases and 250,000 to 500,000 deaths annually.

• Antigenic shift: Influenza viruses (RNA) are constantly evolving, leading to seasonal epidemics.

• Diagnostic advances: Rapid diagnosis via Polymerase Chain Reaction (PCR).

• Epidemiology:

  • High contagiousness: Transmission primarily occurs through airborne droplets during close contact.
  • Epidemic range: Can affect 30-60% of susceptible individuals within a population.
  • Antigenic variation: The unpredictable nature of influenza viruses hinders lasting immunity and makes vaccination challenging.
  • Reservoir animals: Evidence suggests animal sources, such as birds/pigs, play a role in new virus emergence.
  • Epidemic patterns: Pandemic outbreaks occur due to abrupt shifts in the virus's surface antigens. A period of regular seasonal influenza is interspersed with these periodic pandemics.

• Historical Overview:

  • Spanish Flu (1918-1919): Large-scale global pandemic with an estimated death toll of 30 million to 100 million.
  • Asian Flu (1956-1968): Originated in China, believed to have mutated in waterfowl.
  • Hong Kong Flu (1968-1969): Worldwide pandemic, thought to have originated from animal reservoir.
  • H1N1 pandemic (2009) and ongoing COVID-19: Examples of recent pandemics.

• Clinical Presentation (Common Flu):

  • Incubation: 24-72 hours (average 48h);
  • Initial symptoms: Sudden onset of general malaise, high fever, intense chills, headache, and body aches.
  • Later symptoms: Weakness, lack of appetite, sore throat, cough (often dry ), sensitivity to light, muscle and joint pain, runny nose and eye irritation
  • Clinical signs: Sore throat, reddened throat, swollen glands, labored breathing.

• Clinical Presentation (Complicated Cases):

  • Secondary infections: Bacteria like Haemophilus influenzae, Streptococcus pneumoniae, and Staphylococcus aureus can lead to additional complications.
  • Extra-pulmonary effects: Inflammation of the meninges, heart, kidneys, or central nervous system.
  • Pregnancy: Influenza is potentially detrimental to a fetus when the mother is infected.

• Diagnosis:

  • RT-PCR testing: Detects viral genetic material in respiratory samples.
  • Serology: Identifies antibodies against the virus.

• Treatment:

  • Supportive care: Rest, fluids, and over-the-counter pain/fever relievers.
  • Antiviral medications: (Limited effectiveness in uncomplicated cases, often focused on high-risk patients); may be beneficial in early intervention).
  • Vaccination: Annual preventative measure; recommended for high-risk groups.

• SARS-CoV-2 (COVID-19):

  • Transmission: Primarily via airborne droplets; indirect transmission through contaminated surfaces is also possible.
  • Incubation period: Interval of 2 to 14 days between exposure to the virus and symptoms.
  • Clinical presentation: Can vary from asymptomatic to severe pneumonia, respiratory failure, and death. Common symptoms can include fever, headache, cough, and fatigue.

• SARS-CoV-1: An earlier SARS outbreak with similarities to COVID-19.

• MERS-CoV: Another coronavirus responsible for outbreaks that affect respiratory systems.

• Complications: Severe cases may have serious complications, including pneumonia, acute respiratory distress syndrome (ARDS), and sepsis.