The expected number of new cases of an infection caused by an infected individual, in a population consisting of susceptible contacts only.

The transmission of infectious disease or pathogens. When transmission is within the same species, the mode can be horizontal or vertical (INFECTIOUS DISEASE TRANSMISSION, VERTICAL).

Sudden increase in the incidence of a disease. The concept includes EPIDEMICS and PANDEMICS.

Sudden outbreaks of a disease in a country or region not previously recognized in that area, or a rapid increase in the number of new cases of a previous existing endemic disease. Epidemics can also refer to outbreaks of disease in animal or plant populations.

Communicable diseases, also known as infectious diseases, are medical conditions that result from the infection, transmission, or colonization of pathogenic microorganisms like bacteria, viruses, fungi, and parasites, which can be spread from one host to another through various modes of transmission.

Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.

An acute viral infection in humans involving the respiratory tract. It is marked by inflammation of the NASAL MUCOSA; the PHARYNX; and conjunctiva, and by headache and severe, often generalized, myalgia.

Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.

Statistical formulations or analyses which, when applied to data and found to fit the data, are then used to verify the assumptions and parameters used in the analysis. Examples of statistical models are the linear model, binomial model, polynomial model, two-parameter model, etc.

Insects that transmit infective organisms from one host to another or from an inanimate reservoir to an animate host.

The total process by which organisms produce offspring. (Stedman, 25th ed)

Computer-based representation of physical systems and phenomena such as chemical processes.

Programs of surveillance designed to prevent the transmission of disease by any means from person to person or from animal to man.

The pattern of any process, or the interrelationship of phenomena, which affects growth or change within a population.

Restriction of freedom of movement of individuals who have been exposed to infectious or communicable disease in order to prevent its spread; a period of detention of vessels, vehicles, or travelers coming from infected or suspected places; and detention or isolation on account of suspected contagion. It includes government regulations on the detention of animals at frontiers or ports of entrance for the prevention of infectious disease, through a period of isolation before being allowed to enter a country. (From Dorland, 28th ed & Black's Veterinary Dictionary, 17th ed)

A subtype of INFLUENZA A VIRUS with the surface proteins hemagglutinin 1 and neuraminidase 1. The H1N1 subtype was responsible for the Spanish flu pandemic of 1918.

Epidemics of infectious disease that have spread to many countries, often more than one continent, and usually affecting a large number of people.

Elements of limited time intervals, contributing to particular results or situations.

Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)