K - College of Natural Resources - University of California, Berkeley

Figure captions
Figure 1
Evidence for variation in individual reproductive number ν. (A) Transmission data from
SARS outbreak in Singapore, 2003 (Leo et al. 2003). Bars show observed frequency of
Z, the number of individuals infected by each case; lines show maximum likelihood fits
for Z~Poisson (squares), Z~geometric (triangles), and Z~negative binomial (circles).
(A, inset) Probability density function (solid) and cumulative distribution function
(dashed) for gamma-distributed ν (corresponding to Z~negative binomial) estimated
from Singapore SARS data. (B) Proportion of all transmission due to the most
infectious cases for six diseases of casual contact, based on ˆ values in Table 1. (C)
Proportion of transmission due to the most infectious 20% of cases, for data drawn from
single outbreaks (circles), multiple outbreaks (squares), and long-term surveillance
(triangles). Dashed lines show proportions expected under the 20/80 rule (top) and
homogeneity (bottom). Superscript v indicates a significant level of vaccination in the
affected population; * indicates an outbreak that is probably exceptional for rubella.
Figure 2
Superspreading events (SSEs). (A) Reported SSEs (diamonds) relative to estimated
reproductive number R (squares) for twelve diseases of casual contact. Lines show 5-95
percentile range of Z~Poisson(R), and crosses show the 99 th percentile proposed as
threshold definition for SSEs. Stars represent SSEs with more than one source case.
Other diseases plotted in the top row are: a, Streptococcus group A; b, Lassa fever; c,
Mycoplasma pneumonia; d, pneumonic plague; e, tuberculosis. See data in Table S1.
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