A disease refers to an abnormal condition that affects the structure and function of part or whole of an organism. This eventually manifests in certain signs and symptoms which can be medically checked.

Types of Infectious Disease

▪️ Acute Disease:- This develops rapidly and runs its course quickly.

▪️ Chronic Disease:- This develops more slowly, is usually less severe, and persists for a long period.

▪️ Latent Disease:- This is characterized by a period of inactivity for example the case of Herpes.

▪️ Local Infection:- This is one that is confined to a specific area.

▪️ Systemic Infection:- This is a generalized infection and it affects most of the body.

▪️ Septicemia:- This is where pathogens are present in and multiply in the blood.

▪️ Primary Infection:- This is the initial infection in a previously healthy person.

▪️ Secondary Infection:- This is one that follows a primary infection (for example a bacterial infection following a cold).

▪️ Super Infection:- This is a secondary infection that results from the destruction of normal microflora and often follows the use of broad-spectrum antibiotics.

▪️ Mixed Infection:- This is caused by several species of organisms present at the same time.

Stages of Infectious Disease

1). Incubation Period

This is the time between infection and the appearance of signs and symptoms. Although the infected person is not aware of the presence of an infectious agent, she can spread the disease to others. It is important to know that each infectious disease has a typical incubation period.

2). Prodromal Phase

This is the short period during which nonspecific, often mild, symptoms such as malaise and headache sometimes appear.

3). Invasive Phase

This is the period during which the individual experiences the typical signs and symptoms of the disease eg fever, nausea, rash and cough. During the later part of this phase, signs and symptoms reach their greatest intensity.

In some diseases this phase may be sudden and severe, while, in others it may be persistent or chronic. A period of chills followed by fever marks the peak of many diseases. The battle between pathogens and host defenses is at its height during this stage.

4). Decline Phase

Here, symptoms begin to subside as the host defenses and the effects of treatment, if being administered, finally overcome the pathogen. Secondary infections may also occur during this phase.

5). Convalescence Period

During this stage, tissues are repaired, healing takes place, and the body regains strength and recovers. Individuals no longer have disease symptoms, but they may still be able to transmit pathogens to others.