Once a person has contracted SARS, the first symptom that they present with is a fever of at least 100.4 or higher. The early symptoms last about 2-7 days and include non-specific flu-like symptoms, including chills/rigor, muscle aches, headaches, diarrhea, sore throat, runny nose, malaise, and myalgia (muscle pain). Next they develop a dry cough, shortness of breath, and an upper respiratory tract infection. At that time, a chest x-ray is ordered to confirm pneumonia. If the chest appears clear and SARS is still suspected, a HRCT scan will be ordered, because it is visible earlier on this scan. In severe cases, it develops into respiratory failure and acute respiratory distress syndrome (ARDS), and in 70-90% of the cases, they develop lymphopenia (low count of white blood cells). The incubation period for SARS-CoV is from 2-10 days, sometimes lasting up to 13 days, with the mean being 5 days. This means that it can take between 2-10 days for the disease to manifest itself, once you have been exposed to the Coronavirus. The disease progresses in the following way. First you are exposed to the virus, and somewhere between 2-10 days you contract it. Next, the IgM antibody titrates to the SARS-CoV, then peaks during the acute or early convalescent phase (week 3) and declines by week 12. IgG peaks at week 12.