Key messages

  • Infectious diseases are spread from one person to another, or from an animal to a person.
  • Pandemic influenza and large-scale vector-borne diseases, food-related illness and water-borne diseases can require an emergency response.

Infectious diseases are spread from one person to another or from an animal to a person. The spread of a communicable disease usually happens via airborne viruses or bacteria (for example, by coughs and sneezes), but disease can also spread through contact with blood or other bodily fluid.

Pandemic influenza and large-scale vector-borne diseases, food-related illness and water-borne diseases can require an emergency response.

Influenza pandemic

Influenza is commonly known as the flu. An influenza pandemic occurs when a highly infectious new strain of flu emerges for which humans have little or no immunity. During a pandemic, the virus spreads rapidly around the world causing high rates of illness and death and resulting in severe social and economic disruption.

Pandemic influenza can require an emergency response. Check the pandemic influenza page for more information about international, national and state plans to respond to pandemic influenza.

Vector-borne diseases

Vector-borne diseases occur when vectors (living organisms such as bloodsucking insects) transmit infectious diseases between humans or from animals to humans. Vector-borne diseases can be spread by mosquitoes, ticks, flies, sandflies, fleas, triatomine bugs and some freshwater aquatic snails.

The following vector-borne diseases can require an emergency response:

Avoiding vector-borne diseases

Food-related illness and water-borne diseases

The most frequent causes of food or water-borne illnesses are various bacteria, viruses and parasites. Disease can be spread through:

  • raw or undercooked poultry
  • raw or undercooked meat
  • raw or lightly cooked fish, shellfish or other seafood
  • raw milk
  • food contaminated by faecal matter
  • foods contaminated by infected food handlers
  • untreated water 
  • untreated water contaminated by human faeces.

The following food and water borne diseases can require an emergency response:

Zoonotic and other diseases can also require an emergency response.

Zoonotic diseases

Other diseases

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