At this stage of the disease process, the pathogen establishes itself on or within the host. It gains a proper niche which allows it to thrive and reproduce. There are no symptoms and the host is absolutely unaware of the infection. Future techniques in molecular biology may allow us to detect diseases at this early stage when it is vulnerable. Sometimes in this stage, the host detects the disease once it is large enough and stages a successful counter-attack.
The incubation period is basically the amount of time it takes the pathogen to establish itself within the host to the point where symptoms actually appear. The incubation period depends on the disease: for most bacteria it takes 2 to 5 days, but for others like TB or leprosy it could take up to 20 or 30 years.
These are the first symptoms that clearly demonstrate a disease. There is not a set group of initial symptoms because they vary greatly on the patient and which disease they may have. Asymptomatic diseases (in which a patient has no symptoms) are extremely common, as the patient may have antibodies in production for a disease but have never been clinically diagnosed with that disease.
The acute stage is when the disease is at its fullest. At this point, the patient is visibly ill and has true clinical symptoms. During this stage, the intensity of the illness can be seen. This intensity varies with the disease, the strain of the virus or pathogen, and the patient's condition. Because of this, every single infectious disease is survivable, but all of them may also prove fatal to some people.
Many factors determine what symptoms and outcome every disease brings. These factors include:
Diseases are very unpredictable because of all of these factors. They must be analyzed day by day, through statistical data.
This is the period of the disease process in which all of the symptoms decline and the patient recovers. There are six major paths that the recovery can take: