• EPIDEMIOLOGY (GENERAL)
• SEXUAL HEALTH
• CONTROL PROGRAMS

Outbreaks happen for a reason. Just like planes crash for a reason. And determining the reason why an outbreak occurred helps us prevent them in the future. This issue of the journal is devoted to outbreaks of STIs and includes articles that explore epidemics, clusters, changes in antibiotic resistance, changes in behaviours that increase the chance of outbreaks, as well as considering how we respond to and describe outbreaks (Shanka, Thomas, Li, Foster, Smith, Gilbart, Chisholm, Bourne, Oulfon, De Silva).

The first question is what is an outbreak? Last's Dictionary of Epidemiology describes outbreaks as ‘epidemics’ which ‘are events clearly in excess of normal expectancy’.1 Complex statistical techniques can be used to detect outbreaks, but often, as is shown in Figure 1 in the paper by Thomas et al and Figure 1a in the paper by Li, all that is required is the eye of an experienced public health professional (Thomas, Li).

The term outbreak gives a sense of immediacy to an event, but from a public health perspective gradual increases over time in endemic disease may be more important numerically than epidemics. The paper by Foster et al describes the latter scenario. An astute clinician noticed a change in the risk profile of clients with gonorrhoea, a potential outbreak that transformed to higher-level endemic disease unresponsive to acute outbreak measures (Foster). Surveillance systems …