Transmission potential of smallpox in contemporary populations
Despite eradication 1 , smallpox still presents a risk to public health whilst laboratory stocks of virus remain 2 , 3 . One factor crucial to any assessment of this risk is R 0 , the average number of secondary cases infected by each primary case. However, recently applied estimates have varied too...
Gespeichert in:
Veröffentlicht in: | Nature (London) 2001-12, Vol.414 (6865), p.748-751 |
---|---|
Hauptverfasser: | , |
Format: | Artikel |
Sprache: | eng |
Schlagworte: | |
Online-Zugang: | Volltext |
Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
Zusammenfassung: | Despite eradication
1
, smallpox still presents a risk to public health whilst laboratory stocks of virus remain
2
,
3
. One factor crucial to any assessment of this risk is
R
0
, the average number of secondary cases infected by each primary case. However, recently applied estimates have varied too widely (
R
0
from 1.5 to >20) to be of practical use, and often appear to disregard contingent factors such as socio-economic conditions and herd immunity
4
,
5
,
6
,
7
,
8
. Here we use epidemic modelling
9
to show a more consistent derivation of
R
0
. In isolated pre-twentieth century populations
10
,
11
,
12
with negligible herd immunity, the numbers of cases initially rose exponentially, with an
R
0
between 3.5 and 6. Before outbreak controls were applied, smallpox also demonstrated similar levels of transmission in 30 sporadic outbreaks in twentieth century Europe
1
, taking into account pre-existing vaccination levels
13
,
14
(about 50%) and the role of hospitals in doubling early transmission. Should smallpox recur, such estimates of transmission potential (
R
0
from 3.5 to 6) predict a reasonably rapid epidemic rise before the implementation of public health interventions, because little residual herd immunity exists now that vaccination has ceased. |
---|---|
ISSN: | 0028-0836 1476-4687 |
DOI: | 10.1038/414748a |