Skip to main content

Table 3 Development of similarity criteria

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

Point mutations (n nucleotides)

Similarity probability formula

The probability (expressed as a percent) that two viruses will differ by n or more nucleotides given that they are from the same outbreak.

Average number of viral sequences that would have to be sequenced from the same outbreak to have 1 sequence with n nucleotide changes (1/(a)n)

1 nucleotide

an = a1

17.2%

6.2

2 nucleotides

an = a2

2.96%

38.5

3 nucleotides

an = a3

0.509%

Approx. 250

4 nucleotides

an = a4

0.088%

Approx. 1000

Any changes

 

< 20%

> 5