Incubation period

Incubation period


Incubation period is the time elapsed between exposure to the pathogenic organism and when symptoms and signs are first apparent.

Incubation period of some pathogens are:

  • Varicella (Chickenpox) – usually 14 to 16 days
  • Measles (Rubeola) – usually 10 days from exposure to onset of fever, and 14 days to appearance of rash
  • Rubella (German Measles) – 2 to 3 weeks; usually 18 days
  • Mumps – 2 to 3 weeks; usually 18 days
  • Influenza – 18 to 72 hours
  • Diphtheria – 2 to 6 days
  • Pertussis – usually 7 to 14 days, but not more than 3 weeks
  • Meningiococcal Meningitis – usually 3 to 4 days. but may vary from 2 to 10 days
  • Tuberculosis – the time from receipt of infection to the development of a positive tuberculin test ranges from 3 to 6 weeks, and thereafter, the development of disease depends upon the closeness of contact, extent of the disease and sputum positivity of the source case and host parasite relationship. Thus the incubation period of tuberculosis varies from weeks, months or years.
  • Polio – usually 7 to 14 days
  • Hepatitis A – 15 to 45 days (usually 25 to 30 days)
  • Hepatitis B – 45 to 180 days
  • Hepatitis C – 40 to 120 days
  • Cholera – from few hours up to 5 days, but commonly 1- 2 days
  • Typhoid – usually 10 – 14 days, but it may be as short as 3 days or as long as 3 weeks depending on the dose of bacilli ingested.
  • Amoebiasis – 2 to 4 weeks
  • Ascariasis – about 2 months
  • Filariasis – 8 to 16 months
  • Rabies – highly variable from 4 days to many years but usually 3- 8 weeks
  • Yellow fever – 3 to 6 days (6 days recognized under International Health Regulations)
Exam Question
 

Time interval between invasion of the infection agent and appearance of first sign or symptom is Incubation period.

Incubation period is useful for : –

  • Tracing the source of infection and contacts.
  • Period of surveillance or quarantine
  • Immunization
  • Identification of point source or propagated epidemics
  • Estimating the prognosis of a disease.
  • As a rule, infectious diseases are not communicable during the incubation period, but there are exceptions, for example, measles, chickenpox, whooping cough (pertusis) and hepatitis A are communicable during the later part of incubation period.
  • Epidemiological studies is carried for a period of twice the incubation period.
  • Characteristic of a point source epidemic is that all cases develop within one incubation period.
  • Prognosis of a disease can be given by- Incubation Period.
  • In control of communicable diseases, the period of quarantine in respect of a disease is determined by Incubation period.
  • Incubation period of new disease determined by?Generation time.
  • Leprosy is not targeted for global eradication because of Long incubation period.
  • Shortest incubation period is seen in: Influenza.
  • Incubation period of influenza  is 18-72 hours.
  • Incubation period of swine flu is 1-3 days.
  • Incubation period of rubella is 2-3 weeks.
  • Incubation period of typhoid  is 3-20 days.
  • The incubation period of yellow fever is 3-6 days.
  • Incubation period of Hepatitis A is 2 to 4 weeks.
  • Incubation period of staphylococcus aurues food poi­soning is 1-6 hours.
  • Incubation period of Cholera: few hours upto 5 days
  • Shortest incubation period is for food poisoning from Bacillus Cereus.
  • Following are used as proxy measures for incubation period: Latent period ,Serial interval , Generation time.
  • Incubation period of plasmodium vivax is 10-14 days.
  • Incubation period of chancroid is < 7 days.
  • Incubation period  of Diptheria is 2-5 days.
  • The usual incubation period of pertusis is 7-14 days.
  • Incubation period of syphilis is 10-90 days.
  • Incubation period of measles is 10 days.
  • Average incubation period of AIDS is 10 years.
  • Incubation period of gonorrhoea is 2-8 days.
  • In leptospirosis, the incubation period ranges from 2 to 20 days.
  • In rabies,Incubation period depends on the site of bite,number of bites,animal species.
  • Incubation period of HBV is 45 to 180 days.
  • There is long incubation period in prion disease.
  • Incubation period of scabies is 4 weeks.

Incubation period for B.cereus:

  • Incubation period of emetic type of food poisoning        →   1-5 hours
  • Incubation period of diarrheal type of food poisoning      →  8-16 hours.

The incubation period of gas gangrene depends upon the causative organism :

  • Cl. perfringens       →     10 – 48 hrs (1 to 2 days)
  • Cl. septicum          →     2 – 3 days
  • Cl. novyi                →      5 – 6 days.
Incubation period  of Clostridium Tetani is 6-10 days.
Incubation period of salmonella typhi  is 3-21 days.

The limitation of movement of well persons or animals exposed to communicable diseases for a period usually not longer than the longest incubation period is known as Quarantine.

Don’t Forget to Solve all the previous Year Question asked on Incubation period

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