A cluster of 22 imported malaria cases, 21 caused by Plasmodium falciparum,
was observed among illegal Chinese immigrants in northern Italy in the sum
mer of 2000. The rate of severe disease was high because the patients were
not immune and they sought health-care services late in their illness becau
se of their clandestine status. Recognition of the outbreak was delayed bec
ause no regional alert system among infectious diseases hospitals was in pl
ace.