Skip navigation

Infections from Animals (Zoonoses)

Zoonoses are diseases or infections that can be transmitted naturally between humans and other vertebrate animals and refers to any disease agent that moves into humans from an animal source.
Zoonoses are at the forefront of public awareness, not least through problems arising from bovine spongiform encephalopathy (BSE), foot and mouth disease (FMD) and avian influenza.
A key issue with regard to human health is that many zoonotic agents cause little or no significant disease in animals and are, therefore, generally not of high priority to farmers or veterinary practitioners.
Zoonoses may be characterised as:
  • Diseases of animal origin but where transmission to humans is a rare event, but once it has occurred, the cycle can be maintained through human-to-human transmission, e.g. HIV or SARS
  • Diseases of animal origin in which direct or vector-borne animal-to-human transmission is the usual source of human infection, e.g. Lyme borreliosis, leptospirosis
  • Food and water-borne diseases, the occurrence of which has in many cases changed in recent years.
Wildlife is the reservoir of a great many infections that affect domestic animals and/or man and is an important potential source of new and emerging zoonotic diseases. Changes in relationships between man, livestock and wildlife, ecological changes and changes in international trade patterns all contribute to the emergence of new diseases.
Other factors that influence the risk of becoming infected with zoonotic pathogens include changes in medicine and industry, a growing cohort of elderly people, greater numbers of immunocompromised individuals, shifts towards urbanisation, changes in animal production systems and changes in land use, all of which alter the dynamic between hosts, vectors and micro-organisms.
Emerging and re-emerging zoonoses are infectious diseases that:
  • are newly recognised
  • are newly evolved
  • have occurred previously but have more recently shown an increase in incidence or expanded into a new geographic, host or vector.
About 60% of known human infections are zoonotic, so it is unsurprising that nearly 75% of the diseases that have emerged over recent decades have an animal source, and are therefore classified as ‘zoonotic’.

Sources of data

There are four main sources of data in the UK which help to build a picture of the burden of zoonotic infection in the human population. These are:
  • Notification of infectious disease (NOIDS) (Not all zoonotic diseases are notifiable under Public Health Legislation)
  • National surveillance schemes for laboratory-confirmed infections (based on voluntary reporting by diagnostic laboratories)
  • National surveillance schemes for general outbreaks of infectious intestinal disease
  • Enhanced surveillance for specific zoonoses

Notification of Infectious Disease (NOIDS)

Notifications relate to clinical disease. All doctors in clinical practice England and Wales have a statutory duty to notify the proper officer of the local authority of all clinically diagnosed cases of diseases specified under the Public Health (Infectious Diseases) Regulations 1988. New regulations for the Notification of Infectious Diseases in Wales came into force on 26 July 2010.
More information about NOIDS is given on the website of the Health Protection Agency at: and in Wales at:

Major food-borne and water-borne zoonoses

A national surveillance study in England and Wales showed that one in five people develop infectious intestinal diseases each year. Numerically, food and waterborne zoonoses are the most common, they are also Statutorily Notifiable under the Public Health (Infectious Diseases) Regulations 1988, as a cause of food poisoning (see:
In terms of disease burden the most important pathogens were Campylobacter spp, Salmonella spp, Clostridium perfringens, Verocytotoxin-producing Escherichia coli (VTEC) O157, Cryptosporidium spp and Listeria monocytogenes.

Enhanced surveillance

From time to time additional data are collected or specific surveillance studies set up, either nationally or locally, to provide information on certain aspects of a zoonotic disease.

Last updated: 20/09/2011