Arboviral diseases, ISS records 265 dengue cases and a cluster of twenty in the Livorno area

The national arboviral disease surveillance system, coordinated by the Istituto Superiore di Sanità together with the Ministry of Health, publishes two separate series with different closing dates. Reading them together requires attention, because they do not photograph the same day.

Dengue: 265 cases, 24 autochthonous. From January 1 to September 8, 2026, surveillance recorded 265 confirmed cases of dengue, 24 of which autochthonous, with no deaths. 56% of imported cases have the Maldives as place of exposure. Two episodes of local transmission have been identified: the largest is a cluster of 20 confirmed and symptomatic cases with exposure in the province of Livorno, on which epidemiological investigations and disinfestation activities are reportedly under way. The data are taken up by Saluteh24 and by LivornoToday on the basis of the Institute’s note and bulletins, available on EpiCentro’s arboviral disease bulletin page.

The comparison with the previous survey indicates the speed of the movement: as of August 30 confirmed dengue cases were 227 and autochthonous cases only 3 — two in Puglia and one in Tuscany. In just over a week, the “autochthonous” figure thus goes from 3 to 24, and the jump is almost entirely explained by the cluster in the Livorno area. In the same period, publication of the dengue update became weekly: a change in frequency that in itself increases the number of surveys, and which should be kept in mind when comparing two bulletins.

The other two arboviral diseases monitored within the same framework: 25 confirmed cases of chikungunya, one of which autochthonous, and 3 cases of Zika virus, all associated with travel abroad.

West Nile: 521 confirmed cases, 269 neuroinvasive. The ISS’s sixth weekly bulletin, updated to September 2, 2026, records 521 confirmed cases of West Nile virus infection in humans, against 432 in the previous report. The neuroinvasive form affects 269 people, and it is within this subset that the bulletin places four imported infections, with exposure indicated in the Maldives, France, Belgium and Greece. The remaining entries in the count are distributed as follows: 70 asymptomatic positive cases emerging from blood donor screening; 179 people with febrile illness, one of whom with exposure in Burkina Faso; 2 cases with other types of symptoms and one further case with no symptoms. The summary is taken up by the Italpress agency based on the ISS bulletin (Benessere Magazine).

How to read these numbers. These are surveillance counts, not prevalence estimates: they record the confirmed cases that reach the system, and therefore depend on how many tests are carried out and how quickly laboratories transmit results. The distinction between imported and autochthonous case is the most informative from a public health standpoint, because only the latter category signals transmission that has occurred on national territory. Finally, the detection of asymptomatic cases among blood donors does not measure spread in the general population: it intercepts a specific group that is already under screening.

What we don’t know. The two series have different closing dates — September 8 for dengue, September 2 for West Nile — and are therefore not directly comparable with each other. The available material does not contain the complete regional distribution of West Nile cases, nor the outcome of epidemiological investigations in the province of Livorno, nor information on the seasonality expected in the coming weeks. This newspaper reports the data and activities declared by health authorities and does not formulate any behavioral recommendation.

The next verifiable check is the following bulletin published by EpiCentro, which will update both series with the weekly frequency now adopted for dengue.