TABLE 2.

Clinical signs and transmission of H3N2v influenza viruses in ferrets

Virus	Exposure groupa	Mean % max wt loss (days)b	Mean max increase in temp (°C) (days)c	No. of animals with nasal discharge/total no. of animals	No. of animals with sneezing/total no. of animals	Mean max viral titer in NW (log10 PFU/ml)d	No. of animals that seroconverted/total no. of animals (HI titer)	pH threshold for fusiong
IA/11	Inoculated	17.0 (6–8)	1.5 (1–2)	2/3	0/3	6.0	2/2e (1,280)	5.6
	DCT	NTf	NT	NT	NT	NT	NT
	RDT	0	0.9 (2–4)	0/3	0/3	<1	0/3 (<10)
OH/12	Inoculated	12.6 (6–7)	1.3 (2–9)	0/6	5/6	6.4	6/6 (640–1,280)	5.6
	DCT	10.5 (8)	1.2 (3–4)	0/3	3/3	6.3	3/3 (1,280)
	RDT	7.8 (8–9)	1.7 (3–5)	0/3	2/3	6.1	3/3 (1,280)
MI/15	Inoculated	13.3 (6–10)	1.2 (2–6)	0/6	1/6	5.4	6/6 (320–640)	5.6
	DCT	9.6 (4–8)	1.6 (4–7)	2/3	0/3	5.5	3/3 (320–640)
	RDT	4.9 (6–8)	1.0 (4–9)	0/3	0/3	<1	0/3 (<10)
OH/16	Inoculated	16.5 (4–10)	1.0 (1–10)	0/6	2/3	6.1	6/6 (1,280)	5.5
	DCT	10.9 (8)	1.4 (3–4)	0/3	2/3	5.8	3/3 (1,280)
	RDT	8.4 (8–13)	1.0 (3–9)	0/3	1/3	4.9	3/3 (1,280)

^aInoculated indicates inoculation intranasally with 10^6.0 PFU. DCT, direct contract transmission model; RDT, respiratory droplet transmission model.

^bPercent mean maximum weight loss from all infected ferrets. The range of days of observation is shown parenthetically.

^cMean maximum temperature increase over the baseline (ranging from 37.6°C to 39.5°C). The range of days of observation is shown parenthetically.

^dMean maximum viral titers in nasal wash specimens from ferrets (log₁₀ PFU per milliliter).

^eOne inoculated ferret was euthanized due to excessive weight loss; therefore, only the remaining two ferrets were evaluated for seroconversion.

^fNT, not tested.

^gThe highest pH to induce at least 50% syncytia in Vero cells infected with H3N2v influenza viruses. The fusion thresholds for influenza viruses (SW/13 and Pan/99) were 5.4 and 5.6, respectively.