Table 3

Transmission route and clinical characteristics of highly contagious diseases

DiseaseTBInfluenzaMeasles, mumps and varicellaAdenovirusCOVID-19
Transmission routesAirborne, ?prolonged contactDroplet, fomite
? airborne
Airborne (measles, varicella), droplets (mumps)Droplet, fomiteDroplet, ?fomite ?airborne
Presymptom transmissionUnclear but less likelyYes, 12 hours before symptom onset, but less contagiousYes (during prodrome but before rash for measles, yes (varicella 1–2 days before rash), yes mumps (2 days before parotitis)Unknown but unlikelyYes
Incubation periodWeeks months1–4 days12–25 days mumps, 10–12 days measles, 10–20 days varicella2–14 days1–14 days (median 4–6 days)
Isolation periodUntil appropriate treatment startedNot knownVaricella: until rash ‘crusted’; measles: until 4 days after rash onset; mumps: ‘from several days before the parotid swelling to several days after it appears’ (PHE)Not known7 days for mild/moderate disease and 14 days for severe disease
  • ?=Uncertain as robust conclusions cannot be formulated from current data.

  • PHE, Public Health England; TB, tuberculosis.