Incubation period Health Dictionary

That period during the menstrual cycle (see MENSTRUATION) when fertilisation of the OVUM is unlikely to occur. OVULATION usually occurs about 15 days before the onset of the menstrual period. A woman is commonly believed to be fertile for about 11 days in each menstrual cycle – in other words, on the day of ovulation and for ?ve days before and ?ve days after this; this would be the eighth to the 18th day of the usual 28-day menstrual cycle. Outside this fertile period is the SAFE PERIOD: the ?rst week and the last ten days of the menstrual cycle. On the other hand, there is increasing evidence that the safest period is the last few days before menstruation. In the case of irregular menstruation it is not possible to calculate the safe period. In any event, the safety is not absolute. (See also CONTRACEPTION.)... safe period

The period elapsing between the time when a person becomes infected by some agent and the ?rst appearance of the symptoms of the disease. Most acute infectious diseases have fairly definite periods of incubation, and it is of great importance that people who have run the risk of infection should know the length of time which must elapse before they can be sure whether or not they are to contract the disease in question. A person who has been exposed to infection is, during the incubation period, technically known as a contact. By isolating and watching contact cases, medical o?cers can often successfully check a threatened EPIDEMIC.

It must be noted that diseases are not communicated to others by a person who is incubating an illness. Some diseases, however, such as MEASLES, become infectious as soon as the ?rst symptoms set in after the incubation period is over; others, like SCARLET FEVER and SMALLPOX, are not so infectious then as in their later stages. The incubation period for any given disease is remarkably constant, although in the case of a severe attack the incubation is usually slightly shortened, and if the oncoming attack is a mild one, the period may be lengthened. All, however, may take a few days longer than the time stated to show themselves (see INFECTION), and several – especially WHOOPINGCOUGH – may be di?cult to recognise in their early stages.

Incubation periods of the more common infectious diseases:

The fore?nger or second digit of the hand.... incubation

The time between initiation of infection and the first shedding of the agent.... latent period

Recurrence at regular intervals of symptoms in malaria, characterised clinically by paroxysms and resulting from the invasion of the blood by new generations of parasites. Periodicity may be quotidian, tertian, quartan or double quartan according to the intervals between paroxysms.... periodicity

An adjective that relates to the tissues around the TEETH.... periodontal

See TEETH.... periodontal membrane

see PYORRHEA... periodontitis

An inherited condition causing recurrent bouts of fever. (See familial Mediterranean fever.)... periodic fever

Any disorder of the periodontium (the tissues that surround and support the teeth).... periodontal disease

The time or times during which the infectious agent may be transferred directly or indirectlyfrom an infected person to another person, from an infected animal to human, or from an infected human to an animal, including arthropods. In diseases such as diphtheria and scarlet fever, in which mucous membranes are involved from the first entry of the pathogen, the period of communicability is from the date of first exposure to a source of infection until the infective microorganism is no longer disseminated from the involved mucous membranes, ie, from the period before the prodromata until termination of a carrier stage, if this develops. Most diseases are not communicable during the earlyincubation period or after full recovery. In diseases transmitted by arthropods, such as malaria and yellow fever, the periods of communicability are those during which the infectious agent occurs in infective form in the blood or other tissues of the infected person in sufficient numbers to permit vector infections. A period of communicability is also to be distinguished for the arthropod vector - namely, that time during which the agent is present in the tissues of the arthropod in such form and locus (infective stage) as to be transmissible.... communicable period

A period past the due date of an insurance premium, during which coverage may not be cancelled.... grace period

See MENSTRUATION.... period

Time of infection (bite) to the first finding of the organism (eg, malaria parasite) in the bloodstrea m, i.e. from the time of infection to time when first diagnostic stages can be detected.... prepatent period

Premonitory period; indicating the approach of a disease.... prodromal period

A rare, inherited condition that affects young people. Periodic paralysis is characterized by episodes of muscle weakness, which vary in frequency from daily to every few years and last from a few minutes to a few hours. In some cases, there is a drop in the potassium levels in the blood; in others, the levels rise. A carbohydraterich meal may trigger an attack. The condition often clears up without treatment by age 40.... paralysis, periodic

See menstruation.... period, menstrual

The branch of dentistry concerned with periodontal disease.... periodontics

See dysmenorrhoea.... period pain

a well-recognized period just after the diagnosis of type 1 *diabetes mellitus when only very low insulin doses are required to control the condition. It lasts from months to a few years but inevitably ends, when dose requirements will increase quite quickly.... diabetic honeymoon period

a group of rare inherited disorders characterized by recurrent attacks of fever and inflammation in the absence of infection. They include familial Mediterranean fever (see polyserositis), tumour necrosis factor receptor-associated periodic syndrome (TRAPS), and the cryopyrin-associated periodic syndrome (CAPS). Causative gene mutations have been identified.... hereditary periodic fever syndromes

the recognized period, either just before or just after a full *cardiac arrest, when the patient’s condition is very unstable and care must be taken to prevent progression or regression into a full cardiac arrest.... peri-arrest period

(PAS reaction) a test for the presence of glycoproteins, polysaccharides, certain mucopolysaccharides, glycolipids, and certain fatty acids in tissue sections. The tissue is treated with periodic acid, followed by *Schiff’s reagent. A positive reaction is the development of a red or magenta coloration.... periodic acid–schiff reaction

a localized abscess that arises in the periodontal tissues and is usually an acute manifestation of periodontal disease. It appears as a pocket of pus in the tissues of the gum but not around the apex of the tooth.... periodontal abscess

a space between the gingival tissues and tooth occurring in periodontitis. See periodontal disease.... periodontal pocket

n. the tissues that support and attach the teeth to the jaw: the gums (see gingiva), *periodontal membrane, alveolar bone, and *cementum.... periodontium

n. the branch of dentistry concerned with the tissues that support and attach the teeth and the prevention and treatment of *periodontal disease.... periodontology

(in neurology) the time of recovery needed for a nerve cell that has just transmitted a nerve impulse or for a muscle fibre that has just contracted. During the refractory period a normal stimulus will not bring about excitation of the cell, which is undergoing *repolarization.... refractory period

a condition in which attacks of sudden weakness and flaccidity occur in patients with *thyrotoxicosis, seen most often in males of Asian descent. The attacks last from hours to days; they can be prevented by potassium supplements and subsequent treatment of the thyrotoxicosis.... thyrotoxic periodic paralysis