Similarly, during a large DF/DHF disease outbreak in Nakhon Pathom province (Central region) in 2001, 8.8% of individuals (age range: 0 years to over 50 years) had an inapparent infection with dengue virus, as determined by IgM positivity, over a 2-month period between March and April. The gene discussed is CD40LG; the disease is dengue disease.