WHAT IS THE PATHOGENIC PERIOD OF THE DISEASE? - BIOLOGY - 2025

The pathogenic period of a disease refers to the moment in which a pathogen or disease enters the host without the body showing symptoms yet.

During this period, cellular, tissue and organic changes take place. When a disease can be transmitted, the pathogenic period begins when the pathogen penetrates to establish itself in an organism.

Flu virus

The pathogenic stage is characterized by appearing in the environment, just after the human being is affected. Here, there is an interaction between the pathogen, the host, and the environment.

In the pathogenic period, the subclinical and clinical manifestations of a particular disease begin to appear. For these reasons, it can be said that the pathogenic period is the disease itself. Initially, the host agent relationship occurs on a subclinical level.

Later, symptoms that depend on the host and the agent's degree of aggressiveness will begin to manifest; typically the picture of the disease.

It can be said that this period ends when the symptoms referring to the clinical picture end, either because the disease ended because it was cured or because death occurred in the development of the pathological process.

The pathogenic period is divided into the incubation period or the latency period

Incubation period

The incubation period is the time elapsed between exposure to a pathogen, chemical, or radiation, until symptoms and signs are apparent.

In a typical infectious disease, the incubation period refers to the period it takes for the multiple organisms to reach a sufficient quantity to produce symptoms in the host.

For example, a person may be the carrier of a disease, such as strep throat, without exhibiting any symptoms. Depending on the disease, this person may or may not be contagious during the incubation period.

During this period, an infection is subclinical. When it comes to viral infections, the virus replicates in latency. If a disease is infectious, it begins at the time of infection by the infectious agent; it can manifest with a special serological marker, or with a particular symptom.

The intrinsic incubation period refers to the time it takes for an organism to complete its development within its definitive host.

On the other hand, the extrinsic incubation period is the time it takes for an organism to complete its development within its immediate host.

The factors that determine the specific incubation period depend on multiple factors including: the dose of the infectious agent, the route of inoculation, the frequency of replication of the infectious agent, and the immune response and / or sensitivity of the host.

Examples of incubation periods in humans

Due to inter-individual variation, the incubation period is always expressed as a range. When possible, it is best expressed in percentiles, although this information is not always available.

In many conditions, incubation periods are longer in adults than in children or infants.

• Cellulite: between zero and one day.
• Cholera: between 0.5 and 4.5 days.
• Common cold: between one and three days.
• HIV: between two to three weeks, months, or longer.
• Tetanus: between seven to 21 days.
• Rabies: between seven to 14 days.
• Smallpox: between nine and 21 days.

Latency period of viruses

When a disease belongs to the degenerative category, it can be referred to as latency. This means that its evolution is slow, occurring over months or even years.

Viral latency is the ability of a pathogenic virus to remain dormant (latent) within a cell, denoted as the lysogenic part of the viral life cycle.

It can be said that latency is the period it takes between exposure until the first adverse effects appear.

Many scientists define the latency period as the period of time that elapses between exposure to a pathogen or disease-causing agent, and the time when symptomatic disease appears.

If a disease manifests itself with the appearance of a symptom, it can be said that the latency period is the same as the incubation period. The incubation period is usually used for infectious diseases.

A latent viral infection is a persistent type of viral infection that is distinguished from a chronic viral infection. Latency is the phase in which certain virus life cycles, after the initial infection, stop spreading their viral particles.

However, the viral genome is not completely eradicated. The result of this is that the virus can reactivate itself and continue to produce large amounts of viral progenia without the host being affected by new external virus.

This is denoted as the lytic cycle of the viral life cycle and remains within the host indefinitely. Viral latency should not be confused with clinical latency during the incubation period, since the virus is not dormant.

Examples of latency in diseases

An example of a latency period for a disease can be cancer and leukemia. This disease is estimated to have a latency period of about five years before leukemia develops and that it may take an additional 20 years for malignant tumors to appear.

The latency period in cancer is also defined as the time that passes between exposure to a carcinogen (such as radiation or a virus) and the time when symptoms appear.

It should be noted that diseases with long latency periods make its detection difficult and lengthened.

Short latencies related to acute exposures can be expressed in seconds, minutes or hours. On the other hand, chronic exposures have long latencies, of days or months.

References

1. Natural history of disease. Recovered from wikipedia.org
2. Incubation period. Recovered from wikipedia.org
3. Latency virus. Recovered from wikipedia.org
4. The latency period in RNQB (2017). Recovered from cbrn.es.