Table 2. Serum specimens for antibody testing.

Patient classification	Acute phase serum	Recovery phase serum
Confirmed or suspect cases	Blood specimens on the day of hospitalization within 7 days of onset	Blood collected 14 days after the acute phase specimen; the second recovery phase specimen is collected after a 7-day interval
Confirmed or suspect cases when sera is not collected within 7 days of onset	None	Blood collected 14 days after the appearance of symptoms
Close Contact cases	Blood collected within 14 days of the final day of exposure	Blood collected 14 days after the acute phase specimen; the second recovery phase specimen is collected after a 7-day interval
Close Contact cases when sera is not collected within 14 days of onset	None	Blood collected 14 days after the final day of exposure