Figure 2. Propagation of Middle East respiratory syndrome coronavirus (MERS-CoV) in domestic pigs. We inoculated pigs intranasally and intratracheally with 106 tissue culture infectious dose 50 (TCID50) of MERS-CoV isolate hCoV-EMC/2012 or, for controls (mock-inoculated), with Dulbecco’s modified Eagle medium. A) Mean bodyweight gain comparison between mock-inoculated and MERS-CoV–inoculated animals over time. Error bars indicate SDs. B) Mean viral loads shed from the nose and throat determined at the time points indicated by quantifying virus on nasal and throat swabs collected from MERS-CoV–inoculated animals using quantitative reverse transcription PCR (11); in each run, standard dilutions of a titered virus stock were run in parallel to calculate TCID50 equivalents. Error bars indicate SDs. C) Viral loads in tissues collected from MERS-CoV–inoculated animals on days 4 (closed blue circles) and 11 (open red circles) postinoculation. Viral loads were determined as in panel B. Vertical bars indicate means. D) Serum samples collected from pigs at the time of euthanasia (days 4 and 11 postinoculation) and tested for MERS-CoV antibodies by using an ELISA for MERS-CoV spike 1 protein. Antibody titers are plotted as the reciprocal of the last serum dilution positive by ELISA. Horizontal bars indicate means. LN, lymph node.