An increasing incidence of chickenpox central nervous system complications in children: What's happening in Tuscany?

BackgroundThe most frequent noncutaneous site of involvement of chickenpox is the central nervous system (CNS) and complications include cerebellar ataxia, encephalitis, and meningitis.ObjectivesWe have recently observed an unusually high number of children with chickenpox CNS complications in our university children's hospital. A study to evaluate the incidence of these complications over time in children living in Tuscany was carried out.Study designWe evaluated all cases of chickenpox and chickenpox complications leading to hospitalization in children aged 1 month–14 years reported to the Tuscany public health centre between 1997 and 2004. The International Classification of Disease Ninth Revision-CM hospital discharge diagnostic codes and medical records were used.ResultsThe incidence (95% confidence interval) of CNS complications/1000 chickenpox cases was stable between 1997 and 2001 [1997: 0.80 (0.29–1.74); 1998: 0.73 (0.29–1.50); 1999: 0.67 (0.25–1.46); 2000: 0.56 (0.15–1.44); 2001: 0.59 (0.16–1.50)] but increased significantly (χ2 for trend: 9.401; p = .0021) in 2002 [1.56 (0.83–2.66)], in 2003 [1.73 (0.95–2.90)] and in 2004 [1.51 (0.74–2.27)]. Non-CNS complications remained stable over time.ConclusionsPossible factors biasing the result were taken into account. Reasons of increased CNS complications remain unknown, but the possible emergence of a particularly neurotropic strain of varicella-zoster virus should be further investigated.