The key difference between window period and incubation period is that window period is the time between infection and the lab test which can identify the infection while incubation period is the period between infection and onset of the disease.
An infectious disease is a disease caused by a pathogenic organism such as bacteria, fungus, protozoan and virus. Infectious diseases spread directly or indirectly between people. COVID 19 is an infectious disease that transmits from person to person via respiratory droplets (aerosols) carrying the virus. When considering an infectious disease, there are certain time periods we can define, including incubation period, latent period, window period, period of communicability, etc. It is very important to understand these time periods in order to prevent the spreading of diseases.
CONTENTS
1. Overview and Key Difference
2. What is Window Period
3. What is Incubation Period
4. Side by Side Comparison – Window Period vs Incubation Period in Tabular Form
5. Summary
What is Window Period?
The window period is the time period designed to identify the infection. In other words, the window period of an infectious disease is the time between infection and the lab test that can identify the infection. During the window period, the lab test should reliably identify the infection. However, the window period of a particular disease differs based on the test method and other factors. In some infections, the window period may be shorter than the incubation period. Similarly, it can be longer than the incubation period as well in some diseases.
Figure 01: AIDS Test
In infectious diseases, when antigens enter the body, antibodies are developed against them within the body. Therefore, in antibody-based testing, the window period is dependent on the time taken for the development of antibodies. For example, the window period of HIV can be defined as the time between HIV infection and when the test will give an accurate result. It is approximately three months. However, even during the window period, an HIV test can show false-negative results due to the inability to produce a measurable amount of antibodies.
What is Incubation Period?
Incubation period is the time between exposure to the infectious agent and the first appearance of the signs and symptoms of the disease. In other words, it is the time period between exposure to the pathogen and the onset of the disease. During the incubation period, the infectious agent replicates within the host organisms. It multiplies and reaches the threshold in order to produce the symptoms of the disease in the host organism.
Figure 02: Incubation Period
For example, the incubation period of novel coronavirus SARS CoV-2 which causes COVID 19 is 2 to 14 days. It means once you are exposed to SARS CoV-2, within 2 to 14 days, disease symptoms may appear. However, the incubation period may differ among individuals.
Also, the incubation period differs among the different types of infectious diseases. Moreover, depending on the disease, the infected person may or may not be contagious during the incubation period.
What is the Difference Between Window Period and Incubation Period?
The window period is the time between infection and when lab tests can identify the infection. On the other hand, the incubation period is the time between exposure to the infectious agent and the onset of the disease. So, this is the key difference between window period and incubation period. Also, the window period may or may not be longer or shorter than the incubation period. Furthermore, during the window period, the host organism should develop antibodies against the infectious agent, but during the incubation period, the pathogen multiplies in order to make the disease.
The below infographic tabulates the difference between window period and incubation period.
Summary – Window Period vs Incubation Period
The window period is the time between infection and the accurate identification of the infection by a lab test. In contrast, the incubation period is the time between infection and the appearance of symptoms. Thus, this is the key difference between window period and incubation period. In order to identify the pathogen, it is necessary to detect the antibodies developed against the infection during the window period. But, during the incubation period, antigen multiplies and makes many copies in order to make the disease.
Reference:
1. “Incubation Period”. En.Wikipedia.Org, 2020, Available here.
2. “Window Period”. En.Wikipedia.Org, 2020, Available here.
Image Courtesy:
1. “Tobias-AIDS-test” (Public Domain) via Commons Wikimedia
2. “Concept of incubation period” By Patilsaurabhr – Own work (CC0) via Commons Wikimedia