Diagnosis of Imported Dengue and Zika Virus Infections in Italy from November 2015 to November 2022: Laboratory Surveillance Data from a National Reference Laboratory
Christina Merakou,
Antonello Amendola,
Claudia Fortuna,
Giulia Marsili,
Cristiano Fiorentini,
Claudio Argentini,
Eleonora Benedetti,
Gianni Rezza,
Francesco Maraglino,
Martina Del Manso,
Antonino Bella,
Patrizio Pezzotti,
Flavia Riccardo,
Anna Teresa Palamara,
Giulietta Venturi,
The Arbovirus Working Group
Affiliations
Christina Merakou
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Antonello Amendola
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Claudia Fortuna
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Giulia Marsili
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Cristiano Fiorentini
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Claudio Argentini
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Eleonora Benedetti
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Gianni Rezza
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Francesco Maraglino
General Directorate for Health Prevention, Prevention of the Communicable Diseases and International Prophylaxis, Ministry of Health, 00144 Rome, Italy
Martina Del Manso
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Antonino Bella
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Patrizio Pezzotti
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Flavia Riccardo
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Anna Teresa Palamara
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Giulietta Venturi
Department of Infectious Diseases, Italian National Institute of Health (ISS), 00161 Rome, Italy
Dengue (DENV) and Zika (ZIKV) viruses are mosquito-borne human pathogens. In Italy, the presence of the competent vector Aedes albopictus increases the risk of autochthonous transmission, and a national plan for arboviruses prevention, surveillance, and response (PNA 2020–2025) is in place. The results of laboratory diagnosis of both viruses by the National Reference Laboratory for arboviruses (NRLA) from November 2015 to November 2022 are presented. Samples from 655 suspected cases were tested by both molecular and serological assays. Virus and antibody kinetics, cross-reactivity, and diagnostic performance of IgM ELISA systems were analysed. Of 524 cases tested for DENV, 146 were classified as confirmed, 7 as probable, while 371 were excluded. Of 619 cases tested for ZIKV, 44 were classified as confirmed, while 492 were excluded. All cases were imported. Overall, 75.3% (110/146) of DENV and 50% (22/44) of ZIKV cases were confirmed through direct virus detection methods. High percentages of cross reactivity were observed between the two viruses. The median lag time from symptoms onset to sample collection was 7 days for both DENV molecular (range 0–20) and NS1 ELISA (range 0–48) tests, with high percentages of positivity also after 7 days (39% and 67%, respectively). For ZIKV, the median lag time was 5 days (range 0–22), with 16% positivity after 7 days. Diagnostic performance was assessed with negative predictive values ranging from 92% to 95% for the anti-DENV systems, and of 97% for the ZIKV one. Lower positive predictive values were seen in the tested population (DENV: 55% to 91%, ZIKV: 50%). DENV and ZIKV diagnosis by molecular test is the gold standard, but sample collection time is a limitation. Serological tests, including Plaque Reduction Neutralization Test, are thus necessary. Co-circulation and cross-reactivity between the two viruses increase diagnostic difficulty. Continuous evaluation of diagnostic strategies is essential to improve laboratory testing.
