A disease outbreak occurs when more cases of a particular disease occur in a community or geographical area than would normally be expected. Diseases can spread through direct contact, airborne transmission when infectious particles suspended in the air attach to a surface (such as clothing or skin), ingestion of contaminated food, water, or blood, and vector borne transmission via insects like mosquitoes, ticks, and fleas. Human behaviours nearly always contribute to the maintenance and propagation of disease outbreaks, which can have a major impact on human health and economic development.
When disease outbreaks are reported, the Centers for Disease Control and Prevention (CDC) evaluates surveillance information and determines what actions to take. CDC may offer support in the form of diagnostics, drugs, vaccines, or other tools to help local investigators contain and control the outbreak.
Communities that are unable to respond quickly to an outbreak are at risk of suffering disproportionately from its impacts. This includes older people with underlying health conditions, poorer communities, migrants, and women. Communities also suffer when health care facilities are overwhelmed and unable to cope.
A key aspect of outbreak response is to engage with affected populations and to encourage them to alter behaviours that can propagate the disease. As such, anthropologists and communication experts are now routinely included in outbreak response teams. This has proven effective in promoting health literacy, changing traditional burial practices, and reducing the use of mosquito breeding sites during the W. Africa Ebola and Zika epidemics.