This first period is called the incubation period. This occurs from the moment a pathogen enters your body until the first minor symptoms occur. The second period is called the prodromal period; this begins when the first minor symptoms occur until major symptoms occur due to the pathogen creating the infection. Some minor symptoms are headache, nausea and dizziness. The third period is the period of illness; that's when the main symptoms appear because the infection is growing. Some of the main symptoms are diarrhea, vomiting and inflammation. If a patient is infected with a lethal pathogen, they may be at risk of dying during the course of the illness if they are not treated immediately with antibiotics. The fourth period is the period of decline; this is when the symptoms begin to disappear. The fifth and final period is called the convalescence period; this is when the previously infected patient regains his strength and is