WEST NILE VIRUS - EURASIA (07): ITALY (VENETO)
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Date: Thu 18 Aug 2011
Source: Eurosurveillance 2011; 16 (33) Article 3 [edited]
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http://www.eurosurveillance.org/ViewArt ... leId=19949>
Human cases of West Nile virus Infection in Northeastern Italy, 15
Jun-15 Nov 2010.
[Reported by: L Barzon1,2, M Pacenti2, R Cusinato2, M Cattai2, E
Franchin1,2, S Pagni1,2, T Martello2, S Bressan2, L Squarzon1, A M
Cattelan3, G Pellizzer4, P Scotton5, A Beltrame6, F Gobbi7, Z
Bisoffi7, F Russo8, G Palu <
giorgio.palu@unipd.it>]
Abstract
In 2010, for the 3rd consecutive year, human cases of West Nile virus
(WNV) infection, including 3 confirmed cases of neuroinvasive disease
and 3 confirmed cases of West Nile fever, were identified in
northeastern Italy.
While in 2008 and 2009 all human cases of WNV disease were recorded in
the south of the Veneto region, cases of WNV disease in 2010
additionally occurred in 2 relatively small northern areas of Veneto,
located outside those with WNV circulation in the previous years. WNV
IgG antibody prevalence in blood donors resident in Veneto was
estimated as ranging from 3.2 per 1000 in areas not affected by cases
of WNV disease to 33.3 per 1000 in a highly affected area of the
Rovigo province. No further autochthonous human cases of WNV disease
were notified in Italy in 2010. The recurrence of human cases of WNV
infection for the 3rd consecutive year strongly suggests WNV has
become endemic in northeastern Italy.
Introduction
In Italy, the 1st outbreak of West Nile virus (WNV) infection was
reported in 1998 and occurred among horses in the Tuscany region. The
virus re-emerged in 2008, when equine and human cases of West Nile
neuroinvasive disease (WNND) were notified in the Veneto and Emilia
Romagna regions in northeastern Italy. In Veneto, 6 clinical cases of
WNV infection were identified with disease onset from August-September
2008, and all were from the Rovigo province; 3 further human cases of
WNND were notified in Emilia Romagna in September and October 2008.
Veterinary and entomological surveillance documented that WNV
infection was widespread in the same areas in northeastern Italy, with
notification of 794 equine WNV infections in 251 stables and viral
isolation in resident bird species and mosquitoes. Compared to 2008, a
trend towards an increasing number of human WNV infections and a
spread to a wider geographical area was noticed in 2009, when 17 cases
of WNND were notified in northern Italy, including 6 from Veneto, 9
from Emilia-Romagna, and 2 from the Lombardia region.
In 2009, we isolated the virus from a blood donor and sequenced its
whole genome (Ita09, GenBank accession number GU011992). Phylogenetic
analysis classified the Ita09 isolate as Lineage 1, clade 1a, within
the Mediterranean subtype, which includes the majority of strains
responsible for outbreaks in Europe and in the Mediterranean basin.
The full length genome of WNV Ita09 was almost identical to that of
WNV isolated from 2 magpies the year before in the same area and to
WNV sequences obtained from mosquito pools collected in Emilia-Romagna
in 2009, thus suggesting that WNV might have become endemic in some
areas in northern Italy. In these areas, the presence of the _Culex
pipiens_ vector at high density and resident bird species susceptible
to WNV infection, like magpies, carrion crows, and rock pigeons, could
play an important role in WNV persistence and maintenance during
epizootic periods.
Conclusion
In conclusion, for the 3rd consecutive year, human cases of WNV
infection have been identified in northeastern Italy, suggesting WNV
has become endemic in this area. In addition, in 2010, veterinary and
entomologic surveillance identified WNV circulation in Italian areas
that have not been previously affected by WNV infection. An increased
incidence of WNV infection in humans and horses has been also reported
in other European and Mediterranean countries. This epidemiological
situation urges European countries to enhance surveillance of WNV
disease, mosquito control activities, and implementation of measures
to prevent transmission to humans through blood transfusion and organ
donation.
--
Communicated by:
ProMED-mail
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[Interestingly, ProMED has not received any reports indicating that WN
virus is circulating in Italy this year (2011), nor were cases
mentioned in the recent WHO Global Alert and Response report (see
ProMED-mail archive no. 20110819.2519). However, it is currently still
well within the transmission season. In any event, absence of
detection of virus is not necessarily indicative of absence of the
virus in the region, so it is too early to discard the possibility
that, in fact, the virus has become endemic there. ProMED will be
interested in receiving reports of human or equine cases, or WNV
detection in mosquito vectors.
A HealthMap/ProMED-mail interactive map showing the location of Veneto
can be accessed at <
http://healthmap.org/r/00V7>. - Mod.TY]