Glossary

Adverse season: Period of the year during which climatic conditions are not suitable for spread of vector-borne diseases, usually because temperatures are too low.

Area at risk: The geographical area for which the entry, establishment, spread, persistence and impact of disease are assessed.

Basic reproduction number (R0): The expected number of new infected hosts that follows via one vector step from an initial infected host in a susceptible population.

Current area of distribution: Geographical regions where disease is currently present.

Direct economic losses: Losses directly related to the infected entities, e.g. animals or farms. They include production losses at farm level and costs of control measures, both at farm level and at regional/national level.

Economic consequences: Effects of disease that have monetary consequences for affected private and public bodies.

Endemicity: Long term persistence of an infection, with a constant but often low prevalence of infectious individuals in the population. This is generally induced by the constant inflow of new susceptibles in the population (for example by birth), leading to a constant low force of infection.

Environmental consequences: All adverse effects of the pathogen on the environment including ecological effects that do not directly have an impact on human well-being. The main ecological impacts are effects on biodiversity and nature values and pollution of the environment due to insecticides use to control the vector.

Epidemic size: The expected number of epidemiological units (animals/herds/flocks) that will become infected during an epidemic. Please note that the epidemic can last > 1 year or vector season.

Epidemic spread: Exponential growth of the number of infectious individuals in the population, followed by a decrease in growth of the epidemic due to a declining fraction of susceptibles in the population. Typically an epidemic will result in fade out of disease if the replacement rate (inflow of new susceptibles) is low as compared to the speed at which the epidemic grows.

Epidemiological unit: The unit used to assess transmission, spread, persistence and impact of disease (e.g. animals, herds, flocks).

Establishment of disease: The situation in which the infection has passed from a host via a vector to an indigenous host, while the basic reproduction number R0 is higher than 1, i.e. under the given conditions the infection can spread epidemically.

Extent of spread: Extent to which the pathogen is able to spread in time and space, considering both local dispersal and long-distance spread. Extent of spread is measured by the number of farms or animals infected with the disease and the geographical area affected by the disease and/or imposed control measures.

Fade out analysis: Analysis to evaluate fade out of disease due to depletion of susceptible hosts.

High risk period: Period from first infection until detection of the disease during which spread of the infection is not limited by control measures.

Indirect economic losses: Indirect economic losses are non-host specific and often follow from direct losses. Examples are changes in consumer demand and prices, changes in producer costs or input demands, losses incurred in supplying and processing industries, reduced access to export markets, welfare changes, and impacts on other related markets, sectors and economic entities.

Impact: Evaluated consequence of the disease being present in the area at risk.

Infection generation: Average time span needed to transmit the infection from a host via he vector back to a next generation host.

Livestock hosts: Bovines, small ruminants, equines, pigs, poultry.

Overwintering: Survival of the pathogen during the adverse season in which transmission is limited due to climatic factors.

Pathway: Route along which a pathogen can be introduced into the area at risk.

Persistence of disease: Prolonged presence of a pathogen in the area at risk if no fade out of disease occurs and overwintering is possible. This results in endemicity of disease.

Probability of transmission: The probability that there is a combination of time and location possible within the area at risk, where the reproduction number R0 of the infection is above threshold, i.e. above one, taking into account all uncertainties and unknowns.

Risk region: Region or country where infection is present and from where the infectious agent might spread to the area at risk.

Socio-ethical consequences: All consequences which affect human and animal well-being, other than economic effects, such as human disease burden, animal welfare, mortality and morbidity of pets if affected, the ethical turmoil when (healthy) animals and animal products are destroyed, and the adverse effects on citizens it they cannot go into recreational areas (tourism).

Spread of disease: Transmission of disease from infectious individuals to susceptible individuals, directly, indirectly or by vectors. Spread of vector-borne diseases implies that at least a competent vector is present and that local environmental conditions are suitable for virus replication and spread.

Vector-borne diseases: Disease for which vectors are the primary transmission route.

Vectors: Arthropod vectors, i.e., mosquitoes, midges, ticks, (sand)flies.

Vector season: Period of the year during which climatic conditions are suitable for spread of vector-borne diseases