BRAINCAKEPandemics
Diseases are described by how widely they occur:
• Endemic: always present at a steady level in a particular region, e.g. malaria in parts of Africa.
• Epidemic: a sudden rise in the number of cases, well above normal, in one region or country.
• Pandemic: an epidemic that spreads across several countries or continents, affecting large numbers of people worldwide.
Pandemics are nearly always caused by a new strain of virus to which almost nobody has immunity. New strains arise in two main ways:
Antigenic drift: small mutations gradually change the viral antigens. This causes the regular seasonal outbreaks of flu.
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More in Prokaryotic Cells
- Viruses and Disease
- The Spread of Viral Diseases
- Treating Viral Diseases
- Preventing Viral Diseases
- Vaccination
- Disease Control
- Drug Development
- Ethics
All 31 lessons in Prokaryotic Cells · All Edexcel AS-level Biology topics