Division Epidemiological criteria and epidemiological link

Epidemiological criteria are deemed to have been met when an epidemiological link can be established.

Epidemiological link, during the incubation period, is defined as one of the six following:

• human to human transmission: Any person who has had contact with a laboratory confirmed human case in such a way as to have had the opportunity to acquire the infection,

• animal to human transmission: Any person who has had contact with an animal with a laboratory confirmed infection/colonisation in such a way as to have had the opportunity to acquire the infection,

• exposure to a common source: Any person who has been exposed to the same common source or vehicle of infection, as a confirmed human case,

• exposure to contaminated food/drinking water: Any person who has consumed food or drinking water with a laboratory confirmed contamination or a person who has consumed potentially contaminated products from an animal with a laboratory confirmed infection/colonisation,

• environmental exposure: Any person who has bathed in water or has had contact with a contaminated environmental source that has been laboratory confirmed,

• laboratory exposure: Any person working in a laboratory where there is a potential for exposure.

A person may be considered epidemiologically linked to a confirmed case if at least one case in the chain of transmission is laboratory confirmed. In case of an outbreak of faeco-oral or airborne transmitted infections, the chain of transmission does not necessarily need to be established to consider a case epidemiologically linked.

Transmission may occur by one or more of the following routes:

• airborne, by projection of aerosol from an infected person onto the mucous membranes while coughing, spitting, singing or talking, or when microbial aerosols dispersed into the atmosphere are inhaled by others,

• contact, direct contact with an infected person (faecal-oral, respiratory droplets, skin or sexual exposure) or animal (e.g. biting, touching) or indirect contact to infected materials or objects (infected fomites, body fluids, blood),

• vertical, from mother to child, often in utero, or as a result of the incidental exchange of body fluids usually during the perinatal period,

• vector transmission, indirect transmission by infected mosquitoes, mites, flies and other insects which transmit disease to humans through their bites,

• food or water, consumption of potentially contaminated food or drinking water.