Periods of infectivity

Periods of infectivity for some common infections are listed.

• Mumps: 3 days before salivary gland swelling to 7 days after.
• Chicken pox:
  • period of infectivity of chickenpox or shingles (2):
    • although historically, the infectious period for chickenpox was generally considered as being from 48 hours before, to 4 to 7 days after, onset of rash, a recent review suggested that transmission rarely occurs before the onset of rash, and may continue until all the lesions have crusted over (2)
    • in immunocompetent individuals, as a general rule the infectious period the time should be taken as being from 24 hours prior to rash onset to 5 days after rash. For immunosuppressed individuals, it is harder to generalise and therefore the infectious period should be taken from 24 hours prior to rash onset until all lesions have crusted over
    • shingles infection is primarily transmitted by direct contact with vesicle fluid in immunocompetent individuals but may be transmitted via infected respiratory secretions from immunosuppressed patients. The infectious period for localised and disseminated shingles is considered as the time from onset of rash until all of the lesions have crusted over
• Measles: from the appearance of prodromal symptoms to 4 days after the onset of the rash.
• Rubella: one week before onset of rash until 4 days after.
• Whooping cough: one week after exposure until 3 weeks after onset of symptoms (but only 7 days if antibiotics given).
• Scarlet fever: 10-21 days after the rash onset (but only five days if penicillin given) (3)
• Slapped cheek disease: for up to 14 days before the onset of the rash. A child is no longer infectious once the rash has appeared.

References:

1. UK Health Security Agency. Guidelines on post exposure prophylaxis (PEP) for varicella and shingles (April 2022)
2. Institute for Child Health, Great Ormond Street Hospital for Children NHS Trust.
3. Health Protection Agency (Accessed 20/12/07): Scarlet Fever