The 2022 West Nile virus transmission season underway in Italy

The 2022 West Nile virus transmission season underway in Italy

Worldwide, many international locations expertise seasonal endemic viral infections. In Italy, a seasonal endemic viral an infection is brought on by West Nile virus (WNV). The nation has adopted the distinctive well being method to monitoring the virus, and affirmation of circumstances is completed in line with 4 laboratory standards: isolation of the virus from cerebrospinal fluid (CSF) or blood of the host; detection of viral nucleic acid from CSF or blood; the presence of an immunoglobulin M (IgM) response particular to the viral antigen within the CSF; the presence of excessive titers of viral IgM antibodies and the detection of viral IgG antibodies; and using neutralization for affirmation.

Study: Rapid increase in neuroinvasive West Nile virus infections in humans, Italy, July 2022. Image credit: Kateryna Kon/Shutterstock
Examine: Fast enhance in neuroinvasive West Nile virus infections in people, Italy, July 2022. Picture credit score: Kateryna Kon/Shutterstock

A constructive case meets a minimum of one of many above standards. Viral illness can be categorised primarily based on the presence of a neuroinvasive type of the illness and known as West Nile Neuroinvasive Illness (WNND).

The examine

A latest article printed in Eurosurveillance described seasonal transmission of West Nile virus in 2022 and in contrast human circumstances reported in June-July 2022 with these in 2018.


In 2022, the primary WVN an infection in Italy occurred in birds and mosquitoes in early June. Human an infection with the virus started to be detected on June 19. Human circumstances elevated in July, with two strains of the virus (1 and a pair of) co-circulating concurrently. By August, the virus had contaminated many equines, birds and mosquito swimming pools. The Italian surveillance system recorded 301 confirmed human circumstances of WNV, together with 160 circumstances of WNND. Normally, human infections have been preceded by infections in vertebrates and mosquitoes.

As of July 31, 2022, quite a few human circumstances of WNND – few of which have been deadly –, circumstances of West Nile fever (WNF), blood donors with asymptomatic infections, and circumstances with non-specific signs have been detected. The median age for WNND circumstances was 74 years, and for WNV an infection it was 70 years; the male to feminine ratio was 2:1.

Throughout the epidemic – in the course of the 12 months 2018, till July 31, a decrease variety of infections and fewer deaths occurred in comparison with 2022. The variety of human viral infections in June 2022 elevated by 16, which occurred steadily over 4 weeks. It needs to be famous that WNND circumstances in June 2022 have been increased than in June 2018.

Human WNV an infection had been detected in 25 Italian provinces by July 2022, and viral circulation was evident in 41 provinces by August 2022. The best variety of recorded human circumstances was within the province of Padua.

In 2018, for a similar interval, the virus circulation was decrease and the variety of provinces with human an infection was decrease. In 2022, the unfold of the virus an infection to the south and west was better than in 2018.


Yearly, within the northern areas of Italy, a mean of 60 human circumstances is recorded. The variety of WNV and WNND circumstances in 2022 exceeded the variety of circumstances in 2018. Of the 2 lineages, solely lineage 2 was current within the 12 months 2018. Nevertheless, many circumstances weren’t reported or remained undetected in 2022.

The climatic disparities in Italy between 2018 and 2022 could possibly be on the origin of the variations in focus, amplification and unfold of WNV.

Italy applied quite a few vector management measures following the 2018 outbreak. These deliberate measures have been executed in 2022. Though no circumstances related to transfusion have been found, security measures of the blood exams have been applied in lots of provinces, as a result of enhance in human circumstances. Thus, vector/animal surveillance warnings needs to be heeded extra fastidiously.


WNV transmission in Italy jumped in 2022 in comparison with 2018. The virus is now circulating in European international locations as a result of elevated mobility of individuals – as was the case in the course of the coronavirus pandemic 2019 (COVID-19 ). The adoption of applicable viral mitigation packages is important for Italy, in addition to measures to sensitize the final inhabitants, clinicians and well being personnel for correct prognosis and immediate therapy of the illness.

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