Fig. 1: SARS-CoV-2 infects the upper respiratory tract of ferrets.
Ferrets (n = 4 biologically independent animals) were intranasally inoculated with either 1 × 104 or 1 × 105 p.f.u. 2019-nCoV/USA-WA1/2020. a, Virus titre in nasal lavages collected daily. LOD, limit of detection. b–f, At 4 and 10 d post infection, two ferrets from each group were killed and the infection was characterized. b, Number of infectious virus particles in the nasal turbinates. c, Viral RNA was present in the nasal turbinates of all of the infected ferrets. d, Number of viral RNA copies, determined using quantitative PCR with reverse transcription (RT–qPCR), in select organs extracted from infected ferrets 4 or 10 d after infection. Two lung lobes (right (R.) and left (L.) cranial) per animal; SI, small intestine; LI, large intestine. e, Detection of 2019-nCoV/USA-WA1/2020 RNA in rectal swabs of ferrets inoculated with 1 × 105 p.f.u. RNA was extracted from the rectal swabs and the absolute copy numbers were determined using RT–qPCR. f, Body weight of ferrets, measured daily and expressed as a percentage of their weight at day 0. g, CBC analysis, performed every second day. No noticeable differences were detected for any of the parameters tested, including total white blood cells (WBCs), lymphocytes, neutrophils and platelets. The shaded green areas represent the range of normal Vetscan HM5 laboratory values. h–l, Select interferon and cytokine responses in PBMCs harvested every two days after infection. Analysis by RT–qPCR relative to day 0 for animals infected with 1 × 105 p.f.u. 2019-nCoV/USA-WA1/2020. h,i, The infected ferrets displayed elevated expression of ifn-β (h) and ifn-γ (i). j, Only some animals had moderately elevated levels of il-6. k,l, The interferon-stimulated genes mx1 (k; P = 0.0192 on day 4) and isg15 (l; P = 0.009 and P < 0.0001 on days 2 and 4, respectively) showed a sharp peak on day 4 after infection. The number of independent biological repeats (n, individual animals) is shown for each subpanel. Statistical analysis was performed using a two-way analysis of variance (ANOVA) with Dunnett’s post-hoc multiple comparison test. Symbols represent independent biological repeats (individual animals), lines connect the group mean ± s.d. (a,e–l) and bar graphs show the mean (b–d).
