Temperature screening became a widely adopted practice during the coronavirus pandemic. This method aimed to identify individuals with an elevated body temperature, a common indicator of illness. The basic premise involved checking for fever, a symptom often associated with COVID-19, as an initial public health step. This approach sought to provide a quick, non-invasive way to potentially identify those who might be unwell.
Principles of Temperature Screening
Fever represents a natural biological response where the body’s internal temperature rises above its typical range, usually around 98.6°F (37°C). When the body encounters pathogens, the immune system reacts, signaling the brain’s hypothalamus to increase temperature. This elevated temperature is thought to create an environment less favorable for pathogen growth and enhance immune cell efficiency. For screening, a temperature of 100.4°F (38°C) or higher is generally considered a fever.
Common Screening Methods
Non-contact infrared thermometers (NCITs) were frequently employed for temperature screening. These handheld devices measure infrared radiation emitted from a person’s skin surface, typically the forehead. They offer rapid readings within seconds without physical contact, helping maintain distance.
Thermal cameras, also known as thermal imagers or fever cameras, were another method for temperature assessment in public settings. These cameras detect heat naturally given off by individuals, converting the energy readings into a visual thermal profile. Thermal cameras could scan multiple individuals simultaneously, making them suitable for high-traffic areas. While they measure surface skin temperature, some systems could provide an estimated core temperature.
Accuracy Considerations
Temperature screening faced several challenges that influenced its precision in identifying individuals with COVID-19. A significant factor was asymptomatic and pre-symptomatic cases, where infected individuals might not exhibit a fever, or develop it later in their illness. Studies indicated that a notable percentage of COVID-19 patients did not have a fever upon initial presentation or at any point. This meant temperature checks alone would miss a portion of infected individuals, potentially creating a false sense of security.
Fever can stem from numerous other causes unrelated to COVID-19, such as the common cold, influenza, other infections, or reactions to medications. External factors also affected the accuracy of temperature readings. Environmental conditions like ambient temperature, humidity, wind, and direct sunlight could influence surface skin temperature, leading to variations. Physical exertion prior to screening or a sweaty forehead could also alter surface temperature measurements.
Device calibration and user technique further contributed to variability in results. Non-contact thermometers measure skin temperature, which can differ from the body’s internal core temperature. Factors such as device distance, the specific area scanned, and even age or gender could affect the reading. The lack of a universally precise definition for “fever” across different measurement methods and contexts also added to interpretation complexity.
Broader Public Health Role
Temperature screening was widely implemented in various public and private settings during the pandemic. It became a common sight at entry points for airports, schools, workplaces, and public venues. The visible nature of temperature checks made them a tangible, non-invasive initial measure to promote public safety.
This screening was intended as one component within a broader public health strategy aimed at reducing transmission. It functioned as an initial indicator, prompting further evaluation for individuals with elevated temperatures. Controlling the spread of the virus required multiple interventions, including mask-wearing, social distancing, and widespread testing. Temperature screening was not a standalone diagnostic tool, but a supportive measure to identify individuals for additional assessment and contribute to infection control efforts.