Epidemic

Epidemics occur when an agent and susceptible hosts are present in adequate numbers, and the agent can be effectively conveyed from a source to the susceptible hosts. More specifically, an epidemic may result from:

• A recent increase in amount or virulence of the agent
• The recent introduction of the agent into a setting where it has not been before
• An enhanced mode of transmission so that more susceptible persons are exposed
• A change in the susceptibility of the host response to the agent, and/or
• Factors that increase host exposure or involve introduction through new portals of entry (Centers for Disease Control and Prevention)

Epidemics may be the consequence of disasters of another kind, such as tropical storms, floods, earthquakes, droughts, etc. Epidemics may also attack animals, causing local economic disasters (IFRC).

Accordingly to WHO’s classification, these are the major pandemic and epidemic diseases:

• Chikungunya
• Cholera
• Coronavirus disease (COVID-19)
• Crimean-Congo haemorrhagic fever
• Ebola virus disease
• Hendra virus infection
• Influenza (pandemic, seasonal, zoonotic)
• Lassa fever
• Marburg virus disease
• Meningitis
• MERS-CoV
• Monkeypox
• Nipah virus infection
• Plague
• Rift Valley fever
• SARS
• Smallpox
• Tularaemia
• Yellow fever
• Zika virus disease