Symptomatic infections are apparent and clinical, whereas an infection that is active but does not produce noticeable symptoms may be called in apparent, silent, subclinical or occult. An infection that is inactive or dormant is called a latent infection. An example of a latent bacterial infection is latent tuberculosis. Some viral infections can also be latent; examples of latent viral infections are any of those from the Herpesviridae family. The word infection can denote any presence of a particular pathogen at all (no matter how little) but also is often used in a sense implying a clinically apparent infection (in other words, a case of infectious disease). This fact occasionally creates some ambiguity or prompts some usage discussion; to get around this it is common for health professionals to speak of colonization (rather than infection) when they mean that some of the pathogens are present but that no clinically apparent infection (no disease) is present. Different terms are used to describe infections. The first is an acute infection. An acute infection is one in which symptoms develop rapidly; its course can either be rapid or protracted. The next is a chronic infection. A chronic infection is when symptoms develop gradually, over weeks or months, and are slow to resolve. A sub acute infection is one in which symptoms take longer to develop than in an acute infection but arise more quickly than a chronic infection. A latent infection is a type of infection that may occur after an acute episode; the organism is present but symptoms are not; after time the disease can reappear. A focal infection is defined as the initial site of infection from which organisms travel via the bloodstream to another area of the body.