Fig. 1.

Characteristics of Pan/99 virus infection in guinea pigs. Fourteen guinea pigs were infected intranasally with 10³ pfu of Pan/99 virus. The number of infected animals evaluated on each day varied as follows: day 1, n = 14; days 2 and 3, n = 12; days 4 and 5, n = 10; days 6 and 7, n = 8; days 8 and 9, n = 6; days 10–14, n = 4. At all time points, two mock-infected animals were assessed. (A) Viral titers in nasal washings and lung homogenates. At the indicated time points, nasal washings were collected from all guinea pigs, and two animals were killed and their lungs were removed. Infectious content of nasal wash samples and lung homogenates were then determined by plaque assay (limit of detection was 10 pfu/ml or 30 pfu/g). Nasal wash titers are expressed in pfu/ml, and lung titers are expressed in pfu/g of lung. (B) Change in body temperature over the course of infection. Temperatures were measured twice daily from 2 days before infection to 14 days p.i. The average preinfection temperature for each animal was subtracted from each p.i. temperature to obtain the change in body temperature for each guinea pig; the average change in temperature for all guinea pigs was plotted. (C) Change in body weight over the course of infection. Body weight was assessed daily and is expressed as the average percentage change in body weight for each animal.