Published Date: 1999-05-07 23:50:00
Subject: PRO/AH/EDR> Yellow fever - Bolivia (Santa Cruz) (09): urban: CORRECTION
Archive Number: 19990507.0755
YELLOW FEVER - BOLIVIA (SANTA CRUZ) (09): URBAN: CORRECTION
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A ProMED-mail post
<http://www.healthnet.org/programs/promed.html>
[see: Yellow fever - Bolivia (Santa Cruz) (09): urban today
see also:
Yellow Fever - Bolivia
970311110918
Yellow fever - Bolivia (Santa Cruz): RFI 990210211317
Yellow fever - Bolivia (Santa Cruz) (08) 990326203530
Yellow fever - Brazil (Mato Grosso & Para) 990326203619
Yellow fever threat to Asia
990311215901]
Date: Fri 7 Mat 1999 20:47
From: Marjorie P. Pollack, MD <pmm-mpp@mindspring.com>
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[Never believe what you read in the media without checking the source!
It turns out that the URBAN cases referred to all occurred in late
1997/early 1998 (those in 1998 do not appear to have been reported
previously).
All cases in 1999 were RURAL, & were reported on ProMED-mail, see refs.
above - Mod.JW]
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The Lancet article is on:
http://www.thelancet.com/newlancet/reg/issues/vol353no9164/article558.html
(you can register for free as a non-subscriber and access the article).
The article refers to urban cases that occurred during the period December
1997 and June 1998. The criticism in the article is the lack of vaccination
in the city of Santa Cruz, with a prior history of possible urban yellow
fever cases (the six cases he presents are not clearly urban as some had
been to rural areas and some lived on the outskirts of the city).
The article says:
"Findings Between December, 1997, and June, 1998. In December, 1997, the
laboratories of the Centro Nacional de Enfermedades Tropicales (CENETROP)
confirmed yellow-fever infection in an urban resident.
[see: Yellow Fever - Bolivia 970311110918 - Mod.JW]
In response, we started active surveillance of yellow fever in the city and
the surrounding endemic areas and investigated all reported suspected
cases... Symptomatic yellow-fever infection was confirmed in six residents
of Santa Cruz, five of whom died. Five lived in the southern sector of the
city. Two had not left the city during the incubation period, and one had
visited only an area in which sylvatic transmission was deemed impossible."]
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Excerpts from a commentary on the above Lancet article by Thomas P Monath,
Research & Medical Affairs, OraVax Inc, Cambridge, MA 02139, USA:
Facing up to re-emergence of urban yellow fever
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In today's Lancet, van der Stuyft and colleagues report the first instance
of urban transmission of yellow fever in the Americas in 44 years. The
importance of the report lies not in the size of the outbreak -- which
affected only a few urban residents of Santa Cruz -- but in the
demonstration of susceptibility to outbreaks on a more striking scale.
Residents of densely populated cities and much visited areas in coastal
South America have never been vaccinated. An outbreak there would facilitate
dissemination, which could be widespread since the entire planet is
accessible by air within the incubation period of yellow fever. As van der
Stuyft and colleagues point out, the best defence is to create an effective
immune barrier, which includes visitors to and residents (rural and urban)
of the endemic zone. In Santa Cruz, vaccine coverage rates were only 35-40%,
whereas the herd immunity required to prevent person-to-person
transmission of infection may be 90%.
Yellow fever carries a case-fatality rate of about 20%. [But] [a]lthough
urban yellow fever is a significant threat, the constrained dynamics of
transmission, early recognition of the striking clinical presentation, and
efforts to control the infection should limit the impact of the disease.
There is a pressing need for improved methods to differentiate natural from
artificial infections [vaccinations] and for simple, rapid diagnostic tests
derived from
membrane-based immunoassays and PCR. Laboratory-based surveillance, together
with the prevention and control strategies outlined by van der Stuyft and
colleagues, are the critical defensive measures against the future threat of
urban epidemics.
--
ProMED-mail
<promed@usa.healthnet.org>
[Very many thanks, Marj, for this clarification. But as Tom points out
above, the danger remains -- Santa Cruz is a city in search of a YF
epidemic - Mod.JW]
................................................jw
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