At the end of the incubation period 1 s , the individual becomes infectious and moves to group I. At this point, they display signs and symptoms that include fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, jaundice, dark urine, clay-colored stool and joint pain [26] . The infected individual may recover at a rate c. These dynamics are given by dI dt~s E{(mzc)I: