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CHIKUNGUNYA - ITALY (EMILIA ROMAGNA) (08)
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[The following article in Eurosurveillance provides the latest, and
probably final, summary of the 2007 chikungunya virus epidemic in
Italy. With this article, and the onset of winter[ending the mosquito
sesason], this thread is cut. - Mod.TY]
Date: Thu 22 Nov 2007
Source: Eurosurveillance weekly release, 2007 12(11) [edited]
<http://www.eurosurveillance.org/ew/2007/071122.asp#2>
Laboratory results
------------------
The 1st outbreak of autochthonously transmitted
chikungunya virus (CHIKV) in Europe, which
recently occurred in the province of Ravenna in
north-eastern Italy [1,2], has been completely
controlled: the last case's onset occurred on 28
Sep [2007] in the town of Rimini, and in October
no cases were confirmed. Of the 334 suspected or
probable CHIKV cases involved in the outbreak,
samples were examined of 281 and 204 were
laboratory-confirmed by PCR [polymerase chain
reaction], hemagglutination-inhibition, or both.
Reasonably, the number of laboratory-confirmed
cases most likely constitutes an underestimate of
the extent of the outbreak, since blood or serum
samples were not available for all of the
individuals who fulfilled the clinical and/or
epidemiological criteria of the case-definition.
Geographical distribution of cases
-----------------------------------
Most cases were reported among persons living in
or visiting the initially affected villages of
Castiglione di Cervia and Castiglione di Ravenna.
Also detected were 4 smaller clusters of local
transmission in 4 towns in the same region (that
is, Cervia, Cesena, Ravenna, and Rimini), which
are located 9 to 49 km (5.6-30 mi) from the
initially affected villages. For at least 3 of
the 4 clusters, population movement (that is,
persons who visited the area that was primarily
affected or persons from the primarily affected
area who visited one of the 4 towns) can be
reasonably assumed to have been the main
determinant of local transmission. However, if
this was the case, the question arises as to why
no previous outbreaks of CHIKV occurred in other
Italian regions in 2005-2006 (after the epidemic
in Reunion), when at least 30 infected travellers
returned to locations infested by mosquito vector
populations [3]; the same question arises for
several hundred cases reported among travellers
returning from affected areas to a number of
European countries in the same period [3,4,5].
Possible explanations include: i) high
concentration of vectors in the affected towns;
ii) highly viremic persons exposing themselves to
aggressive _Aedes albopictus_ populations as a
consequence of the structures of houses and/or
behavioural factors (such as, spending time
outdoors in houses' surroundings).
Overall, the epidemic in Italy can be said to be
the result of the combined effect of the
globalisation of vectors and humans, which
occurred through a 2-step process: i) the
introduction and adaptation of the vector _Ae.
albopictus_ to a new environment (that is, a
temperate climate); and ii) the introduction of
CHIKV in a previously infection-free country,
with totally susceptible subjects, as the result
of population movement (that is, travelling human
hosts, acting as a sort of Trojan horse).
However, the epidemic was limited in space and
time, with a marked decay rate since the adoption
of appropriate control measures (albeit they were
taken at different times in different locations).
In addition, there is probably a time-limited
capacity of the vector to sustain infection
transmission beyond the hot season in a country
with a temperate climate.
What did we learn from the Italian epidemic?
--------------------------------------------
- Vector-borne diseases, historically confined to
tropical environments, can be introduced within
Europe if the conditions are appropriate (that
is, the presence of vectors). The major
determinant of the outbreak in Italy was probably
the high vector density at the time of arrival of
the index case, which could be explained by the
lack of preventive vector-control measures in an
area that was considered to be 'infection-free';
- The vectorial capacity of _Ae. albopictus_ for
CHIKV is high [6]. A few hours spent in a highly
vector-dense village by only one feverish patient
caused a large outbreak in a naïve population;
- As seen for other infectious diseases causing
international crises (that is, SARS), population
movement and vector colonisation of new areas are
important determinants of disease globalisation.
Nonetheless, there are still some questions that
need to be investigated further:
- Why did a single case result in an outbreak
while none of the many CHIKV-infected travellers
have caused local transmission upon returning
home to Italy or other European countries in
roughly similar vector-dense areas;
- Has the infection been eradicated in the
affected area or could it reappear at the
beginning of the next hot season due to
overwintering [by infected mosquitoes]?
- What is the probability that other similar
events will occur in Italy or other European
countries where _Ae. albopictus_ is present, and
could other infections, such as dengue, cause
similar outbreaks in Europe?
These questions need to be adequately answered so
as to strengthen activities for the surveillance
and control of _Ae. albopictus_ and other vectors
of exotic infectious diseases (that is,
chikungunya and others) and to perform early
diagnosis of viral agents that can be imported
and transmitted in Europe. Furthermore, more
intense research efforts should be promoted in
Italy and in Europe on the mosquito-virus
relationship, as well as in other critical areas
concerning vaccine and specific antiviral drugs.
Experimental infections in vector populations,
virus and vector genotyping are some of the
specific investigations already planned in Italy.
References
----------
1. Angelini R, Finarelli AC, Angelini P, Po C,
Petropulacos K, Macini P, Fiorentini C, Fortuna
C, Venturi G, Romi R, Majori G, Nicoletti L,
Rezza G, Cassone A: An outbreak of chikungunya
fever in the province of Ravenna, Italy. Euro
Surveill 2007; 12(9): E070906.1. Available from
<http://www.eurosurveillance.org/ew/2007/070906.asp#1>
2. G Rezza, L Nicoletti, R Angelini, R Romi, AC
Finarelli, M Panning, P Cordioli, C Fortuna, S
Boros, F Magurano, G Silvi, P Angelini, M
Dottori, MG Ciufolini, GC Majori, A Cassone:
Infection with Chikungunya virus in Italy : An
outbreak in a temperate region. Lancet, 2007, in
press.
3. Nicoletti L, Ciccozzi M, Marchi A, Fiorentini
C, Martucci P, D'Ancona F, Ciofi degli Atti M,
Pompa MG, Rezza G, Ciufolini MG: Correlates of
Chikungunya and Dengue in travellers. Emerging
Infectious Diseases, in press.
4. Depoortere E, Coulombier D, ECDC Chikungunya
risk assessment group: Chikungunya risk
assessment for Europe: recommendations for
action. Euro Surveill 2006; 11(5): E060511.2.
Available from
<http://www.eurosurveillance.org/ew/2006/060511.asp#2>
5. Joint ECDC/WHO European Risk Assessment on
Chikungunya in Italy: a mission report. Available
from
<http://www.ecdc.europa.eu/pdf/071030CHK_mission_ITA.pdf>
6. Vazeille M, Jeannin C, Martin E, Schaffner F,
Failloux AB: Chikungunya: A risk for
Mediterranean countries? Acta Trop. 2007 Oct 12;
[Epub ahead of print].
--
[R Angelini (1), AC Finarelli (2), P Angelini
(2), C Po (2), K Petropulacos3 G Silvi (1), P
Macini (2), C Fortuna (4), G Venturi (4), F
Magurano (4), C Fiorentini(4), A Marchi (4), E
Benedetti (4), P Bucci (4), S Boros (4), R Romi
(4), G Majori (4), MG Ciufolini (4), L Nicoletti
(4), G Rezza (4), A Cassone <cassone@iss.it> (4)
1. Dipartimento Sanita Pubblica, Azienda Unita
Sanitaria Locale (Department of Public Health,
Local Health Unit), Ravenna, Italy
2. Servizio di Sanita Pubblica, Regione Emilia-Romagna, Bologna, Italy
3. Servizio Presidi Ospedalieri, Regione Emilia-Romagna, Bologna, Italy
4. Department of Infectious, Parasitic and Immunomediated Diseases,
Istituto Superiore di Sanita, Rome, Italy]
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[A map of the Emilia Romagna region and its location in Italy can be
accessed at
<http://www.knowital.com/italy/maps/emiliaromagnamap.html>. - Mod.TY]
[see also:
Chikungunya - Italy (Emilia Romagna) (07) 20071031.3534
Chikungunya - Italy (Emilia Romagna) (06) 20070921.3134
Chikungunya - Italy (Emilia Romagna) (05) 20070918.3102
Chikungunya - Italy (Emilia Romagna) (04) 20070907.2957
Chikungunya - Italy (Emilia Romagna) (03) conf. 20070903.2899
Chikungunya - Italy (Emilia Romagna) (02) conf. 20070902.2889
Chikungunya - Italy (Emilia Romagna): susp. 20070901.2877
Chikungunya, imported, risk of transmission 20070125.0338
Chikungunya - Indian Ocean update (23): sequelae, RFI 20070821.2727
Chikungunya - Indian Ocean update (22): India (West Bengal) 20070815.2671
2006
----
Chikungunya - Indian Ocean update (05): spread to Europe 20060304.0695
Chikungunya - Indian Ocean Update (33): Maldives 20061224.3598
Chikungunya - Indian Ocean update (32) 20061014.2953
Chikungunya - Indian Ocean update (09): islands, India 20060320.0864]
........................................ty/mj/jw
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