[Coral-List] White Plague in PRico

[Drew Harvell]

>Dear Ernesto and other Listers:
>
This is the second report of a Plague outbreak; an earlier one in Nov 
was reported in ST JOhn. Disease outbreaks are expected to follow the 
kind of major bleaching event we just had in the CAribbean (and that 
is developing in Australia) and it is very useful to know when they 
occur after the temperature anomaly begins: are they almost immediate 
as Ernesto reports for Plague, or do they lag until the warmer summer 
months? Ernesto also rightly emphasizes the value of good diagnostics 
and is getting his samples to L. Richardson who has the diagnostic 
probe.

>The final consideration for recording disease outbreaks is to get 
>good quantitative data. It will advance our field if folks with 
>monitoring programs can get numbers of diseased corals at multiple 
>intervals through time, so we can estimate basic epidemiological 
>parameters, like Ro. Ro is the number of new secondary cases 
>generated by each primary infection.   It can be estimated from the 
>slope of the line of increasing cases through time.  The relevant 
>time to measure depends on the rate of new infections, but it could 
>be useful in a rapid outbreak to resample monthly. To call it an 
>outbreak, Ro must be above one. AS examples, Ro for some recent 
>human outbreaks-- SARS: 2-3, HIV: 2-5, smallpox: 5-10, Pandemic 
>Influenza: 5-15.  The higher the Ro, the harder to control.  The 
>high Ro for Smallpox and INfluenza is because they are so rapidly 
>transmissable.
>
>The theory of disease outbreak, transmission and control is 
>discussed in a useful paper about SARS:
>
>Anderson et al., 2003. Epidemiology, transmission dynamics and 
>control of SARS:  the 2002-2003 epidemic. I'll get together some 
>other references on "When is it an Outbreak" and post them on my 
>site in a few weeks.
>
Regards, Drew
-- 
Drew Harvell
Professor
Department of Ecology and Evolutionary Biology
E- 321 Corson Hall
Cornell University
Ithaca, NY 14853

VOICE:  607-254-4274   FAX: 607-255-8088  email:cdh5 at cornell.edu 
http://www.eeb.cornell.edu/harvell/harvell.html