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. 2018 Dec 21;13(12):e0208896.
doi: 10.1371/journal.pone.0208896. eCollection 2018.

Local transmission of chikungunya in Rome and the Lazio region, Italy

Francesco Vairo  1 , Alessia Mammone  1 , Simone Lanini  1 , Emanuele Nicastri  2 , Concetta Castilletti  2 , Fabrizio Carletti  2 , Vincenzo Puro  1 , Domenico Di Lallo  3 , Vincenzo Panella  3 , Donatella Varrenti  4 , Paola Scaramozzino  5 , Antonino di Caro  2 , Paola Scognamiglio  1 , Maria Rosaria Capobianchi  2 , Giuseppe Ippolito  2 ; Chikungunya Lazio Outbreak Group
Affiliations

Local transmission of chikungunya in Rome and the Lazio region, Italy

Francesco Vairo et al. PLoS One. .

Abstract

On September 7, 2017, three potentially autochthonous cases of chikungunya were notified in the Lazio region. An Outbreak investigation based on established surveillance system data and molecular analysis of viral variant(s) were conducted. Epidemiological analysis suggested the occurrence of 3 main foci of local transmission. The major focus involved 317 cases with epidemiological link with the area of Anzio. The other two foci occurred in Rome (80 cases) and Latina (8 cases). Cumulative incidence in Anzio and Latina were 331.4 and 7.13 per 100,000 residents, respectively. Cumulative incidences ranged from 1.4 to 14.3/100,000 residents in Rome. This is the first report of a chikungunya outbreak involving a densely populated urban area in a western country. The outbreak probably started in Anzio, spread by continuity to neighbouring villages, and then to the metropolitan area of Rome and to the Latina area favoured by the touristic nature of the Anzio area.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Case definition flow-chart.
Fig 2
Fig 2. Epidemic curve of autochthonous CHIKV cases by probable place of transmission.
NOTE. Total number of cases reported is 399. Two cases with no epidemiological link with Anzio were residing in two towns in Rome province and one case had not date of symptoms’ onset available. Anzio, cases residing in Anzio or with probable transmission in Anzio; Rome, cases with no epidemiological link with Anzio and with probable transmission in Rome; Latina, cases with no epidemiological link with Anzio and with probable transmission in Latina. Probable place of transmission is defined as the city where the case was continuously residing for the 15 days before the onset of symptoms.
Fig 3
Fig 3. Geographical distribution of cases according to incidence (per 100.000 inhabitants).
NOTE. Incidence has been calculated considering the place of living of the reported cases and not the epidemiological link (history of travel during the 15 days before the symptoms’ onset). *one case linked to Anzio Area is resident in Abruzzo Region.
Fig 4
Fig 4. Phylogenetic tree of the complete genome sequence (A) and polymorphisms in E1 and E2 envelope glycoproteins (B).
A) Phylogenetic tree of the complete genome sequence of the isolate CHIKV/ITA/Lazio-INMI1-2017 obtained from the current outbreak, Lazio region, Italy. The Maximum-likelihood phylogenetic tree was built with the complete genome sequence of the isolate CHIKV/ITA/Lazio-INMI1-2017 (outlined in bold characters) in the context of whole genome sequences representing the 3 major described CHIKV lineages: ECSA (including the Indian Ocean lineage), Asia and Caribbean, and West Africa. These sequences are indicated with their accession number, geographic origin and year of sampling. Asian and Caribbean and West Africa sequences are collapsed to increase the clarity of the figure. Bootstraps were generated using 1,000 replicates; only those >80 are shown. The bar represents genetic distance (substitutions per nucleotide position). B) Polymorphisms in E1 and E2 envelope glycoproteins of CHIKV/ITA/Lazio-INMI1-2017, at positions considered relevant for vector adaptation.
See this image and copyright information in PMC

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