Answer:
STAGE 1: Incubation
STAGE 2: Prodromal
STAGE 3: Illness
STAGE 4: Decline
Explanation:
1. Incubation
The incubation stage includes the time from exposure to an infectious agent until the onset of symptoms.
Viral or bacterial particles replicate during the incubation stage.
Duration
The exact time frame of the incubation stage varies depending on the infection. Here are a few examples:
Flu
The flu virus incubates for 1–4 daysTrusted Source, but symptoms can appear as early as 2 days after the virus enters the body.
Hepatitis B
The incubation period for hepatitis B virus (HBV) ranges from 1.5–6 months.
Salmonella
Salmonella, a common foodborne bacterium, causes symptoms within 6 hours to 6 days. They can include:
- diarrhea
- vomiting
- stomach cramps
2. Prodromal
The prodromal stage refers to the period after incubation and before the characteristic symptoms of infection occur.
People can also transmit infections during the prodromal stage.
During this stage, the infectious agent continues replicating, which triggers the body’s immune response and mild, nonspecific symptoms. These symptoms can include:
- low-grade fever
- fatigue
- Duration
The duration of the prodromal stage varies depending on the type of infection.
For example, the flu has a short incubation period of about 2 daysTrusted Source. As a result, the prodromal stage may overlap with the incubation stage and the onset of illness.
The Centers for Disease Control and Prevention (CDC)Trusted Source state that the virus might transmit to others 1 day before symptoms develop and up to a week after becoming ill.
3. Illness
The third stage of infection is an illness or clinical disease. This stage includes the time when a person shows apparent symptoms of an infectious disease.
Symptoms
The symptoms of infection vary widely depending on the underlying cause.
In general, people who have an active infection may experience:
- fever
- fatigue
- headache
- muscle aches
- swollen lymph nodes
- Respiratory infections
Symptoms of respiratory infections, such as the common cold or influenza, include:
- persistent cough
- runny nose
- sneezing
- sore throat
- difficulty breathing
- Gastrointestinal infections
Gastrointestinal infections can cause the followingTrusted Source symptoms:
- diarrhea
- nausea
- vomiting
- stomach pain
- loss of appetite
Duration
The exact time frame varies depending on the type of infection, the number of infectious microbes in the body, and the strength of a person’s immune system. Here are some examples:
Flu
Symptoms can last up to a week for many viral respiratory infections, such as the flu.
Hepatitis B
Certain infections can last several weeks or even years. Symptoms of hepatitis B can last several weeksTrusted Source. It can also develop into a chronic disease if the infection continues for more than 6 months.
Chickenpox, herpes
The herpes simplex virus (HSV) and chickenpox (VZV) can hide in a dormant state within nerve cells. These viruses can stay in the body for many years before reactivating. If the VZV virus reactivates, it causes shingles.
Chickenpox symptoms usually last between 4 and 7Trusted Source days.
Herpes symptoms vary in their duration depending on the type of infection.
4. Decline
During the decline stage, the immune system mounts a successful defense against the pathogens, and the number of infectious particles decreases.
Symptoms will gradually improve.
However, a person can develop secondary infections during this stage if the primary infection has weakened their immune system.
During this stage, the virus can still transmit to other people.
