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Table 5 Probability that anecdotally-linked outbreaks have a common source based on epidemiological and virological sequence data sequence.

From: Linking healthcare associated norovirus outbreaks: a molecular epidemiologic method for investigating transmission

Pair Variantx Varianty Δ (bases) Description of epidemiological link a b Probability of transmission link
1 1A 1A 0 Doctor exposed on affected ward then worked on another ward while ill. Outbreak began on this ward 1 day later. 1.0 0.38 (23/60) 72%
2 3D 3E 3* Transfer from nursing home into hospital (ward unspecified) 0.004 0.016 (1/60) 20%
3 1H 2M 4** Transfer from hospital to nursing home of primary case 0.001 0.016 (1/60) 6%
4 1A 1A 0 Transfer from hospital to nursing home 1.0 0.38 (23/60) 72%
5 1A 1A 0 Transfer of patient from hospital affected to unaffected wards 1.0 0.38 (23/60) 72%
  1. a Probability that the viruses could be drawn from the same outbreak basic on genetic similarity
  2. b Probability that second virus would randomly be drawn from the viral population
  3. c Probability that outbreaks with anecdotal links had a transmission link: P(x|Type = M) = ca/(ca+(1-c)b)
  4. *3 nucleotide differences in the capsid
  5. ** 1 nucleotide difference in polymerase, 3 nucleotide differences in the capsid