TABLE 1.

Components of laboratory-based, proactive surveillance for dengue and DHF^a

Type of surveillance	Samplesb	Approach
Sentinel clinic and physician network	Blood from representative cases of viral syndrome, taken 3–15 days after onset of illness	Representative samples taken year round and processed weekly for virus isolation and for IgM antibodies
Fever alert system	Blood samples from representative cases of febrile illness	Increased febrile illness in community investigated immediately; samples tested as above
Sentinel hospital systemc	Blood and tissue samples taken during hospitalization and/or at death	All hemorrhagic disease and all viral syndromes with fatal outcome investigated immediately and tested as above

^aEmphasis should be placed on the interepidemic period, using a nonspecific case definition. After an epidemic begins and after the virus serotype(s) is known, the case definition should be made more specific and surveillance should be focused on severe disease. 

^bAll samples are processed weekly for virus isolation and/or for dengue virus-specific IgM antibodies. 

^cSentinel sites should be geographically representative.