Coronavirus patient study raises questions about whether temperature checks work

Back to work: Are workplace temperature checks enough?

Coronavirus patient study raises questions about whether temperature checks work

Public health leaders in many regions are giving a wary OK to slowly reopen businesses and public spaces with best practices to reduce transmission risks. In some areas, workplaces are reopening as government-phased policies permit.

Employers are looking for ways to enhance workplace health and safety, and one popular measure being implemented is temperature scanning checks to look for persons with elevated temperatures, one possible symptom of COVID-19.

But are temperature checks an effective measure to ensure workplace health and reduce risks of contagion?

Casting a net to screen for COVID-19

Mackenzie Weise, an epidemiologist and infection prevention clinical program manager at Wolters Kluwer, commented that temperature checks alone will not be effective and should be considered one of several tools used to identify COVID-19.

She specified that only a subset of infectious cases present with fever and ns the limitations of temperature screening to using a net to catch butterflies. The net may catch some butterflies, but won’t catch them all and other insects may be inadvertently caught.

Similarly, temperature checks can help identify people with high temperatures due to COVID-19, but may also result in false negatives and positives where some COVID-19 cases could go unidentified and some non-cases could be misidentified.

Why do workplace temperature checks often come up short in identifying workers who pose a risk?

A few factors include:

  • Training: Inadequate and inconsistent training for those conducting the checks can lead to improper use of the equipment. Mistakes can be as simple as an incorrect distance between the infrared thermometer and the person being checked — causing averaging errors that lower the temperature. Errors can also arise if the thermometer is aimed at the wrong part of the face — a forehead will be different than eyes near the tear ducts for example.
  • Symptoms: Not all infectious cases present with fever. Also, feverish symptoms can be easy to mask with over-the-counter antipyretic medicine acetaminophen. World health experts also suggest individuals that may not have symptoms may be able to transmit the virus.“As many as 25% of infected individuals may actually remain asymptomatic according to the CDC so that adds to the complexity of temperature screenings for COVID-19,” cautions Mackenzie Weise
  • False results: Even if infrared thermometers are used correctly, there is still a chance of false negatives or false positives caused by environmental factors. Someone sitting in a car near an air conditioning vent just before entering work could chill his or her surface temperature just enough to mask symptoms. Running to avoid being late to work on a hot day or sitting in a hot car just minutes before testing may elevate one’s surface temperature enough for an improperly trained screener to identify a false positive. Another consideration is a stomach bug might be accompanied by a fever, and while that person should not be admitted to work, the false positive may result in unnecessary COVID-19 follow-up and testing.

Temperature checks are not a quick fix

Temperature checks implemented by themselves are not enough. If workplace health and safety managers screen workers, there needs to be a clear set of protocols to manage questions and scenarios encountered.

For those identified as having a fever, says Weise, “Important next steps include promptly isolating infectious individuals from others, connecting them to care and/or testing, and providing clear information on how to prevent additional transmission.

Simply restricting a person from entering a factory or office building due to a fever does not do enough to ensure the safety of the broader community.” Best practice policies and coordination with public health leaders is needed for communities to stay healthy.

If temperature checks are used, they should be leveraged as one way to help people with COVID-19 symptoms receive the care they need.

Screening and privacy concerns

Screening employees and visitors as they enter a workplace may involve an infrared thermometer that takes a reading, but doesn’t record it or associate it with an employee. If any logging of temperatures is done, this raises questions about the protection of worker health data.

Should it be treated patient data? Who is conducting the checks? What will happen to the information collected? Companies should be prepared in advance with a well-defined process and policy that is communicated effectively to address these questions in order to respect worker privacy and to avoid confusion during the temperature check process.

After months of quarantine, employees may be eager to get back to the workplace to restore income or business as usual. A lot is at stake and it’s easy to think of temperature checks as a quick fix to put everyone’s minds at ease in the push to resume pre COVID normalcy.

In reality, temperature screening will only catch some people with COVID-19 some of the time.

While that will alleviate some anxieties, it may foster a false sense of security if workplaces do not also build broader, more comprehensive policies and job site modifications to tangibly reduce transmission risks that can further impact their employees, their businesses and their communities.

Find more COVID-19 resources and information, visit our COVID-19 resource page.


Non-contact Temperature Assessment Devices During COVID-19

Coronavirus patient study raises questions about whether temperature checks work

As states and communities implement reopening plans during the COVID-19 pandemic, non-contact temperature assessment devices may be used as part of an initial check at entry points to identify and triage people who may have elevated temperatures.

Be aware that, even when the devices are used properly, temperature assessment may have limited impact on reducing the spread of COVID-19 infections. Some studies suggest that temperature measurements alone may miss more than half of infected people.

Thermal imaging systems and non-contact infrared thermometers, which are non-contact temperature assessment devices, may be used to measure a person's temperature. An elevated temperature is one way to identify a person who may have a COVID-19 infection, although an infected person may be contagious without an elevated temperature or other easily detectable symptoms.

This page provides information on the use of non-contact temperature assessment devices during the COVID-19 pandemic. For general information on strategies for community mitigation to reduce or prevent local COVID-19 transmission, see the CDC's Implementation of Mitigation Strategies for Communities with Local COVID-19 Transmission.

About Non-contact Temperature Assessment Devices

Establishments such as businesses, transportation systems, and community organizations are developing plans to resume normal or phased operations during the COVID-19 pandemic.

These plans may include an initial assessment to try to identify people who may be infectious to limit the spread of COVID-19 infections. Temperature measurement can be one part of the assessment to determine if a person has an elevated temperature potentially caused by a COVID-19 infection.

One method to measure a person's surface temperature is the use of “no-touch” or non-contact temperature assessment devices, such as thermal imaging systems (also known as thermal imaging cameras or infrared telethermographic systems) or non-contact infrared thermometers.

The use of other temperature assessment devices, such as oral thermometers, requires physical contact which may increase the risk of spreading infection.

The available scientific literature supports using thermal imaging systems and non-contact infrared thermometers to detect elevated temperatures.

 These devices have many benefits, but they must be used properly to get accurate readings.

Since an elevated temperature does not conclusively indicate a COVID-19 infection, further evaluation and diagnostic testing are needed to determine if someone has a COVID-19 infection.

For the FDA's recommendations on the benefits, limitations, and proper use of these devices, see:

Benefits of Non-contact Temperature Assessment Devices

  • These non-contact devices can quickly measure and display a temperature reading so a large number of people can be evaluated individually at points of entry.
  • Non-contact infrared thermometers require minimal cleaning between uses.
  • Using non-contact temperature measurement devices may help reduce the risk of spreading COVID-19 infections.

Limitations of Non-contact Temperature Assessment Devices

Non-contact temperature assessment devices are not effective if used as the only means of detecting a COVID-19 infection. Available scientific literature has identified that effectiveness can be limited by several factors, including:

  • Infections without a fever;
  • Use of fever-reducing drugs;
  • Other infections or conditions that may cause elevated temperatures;
  • Devices failing to identify elevated temperatures, or misreading normal temperatures as elevated;
  • Failure to follow the manufacturer's instructions for use, such as for set-up, operation, and training.

Manufacturer Labeling and Instructions for Use

The manufacturer's labeling for each thermal imaging system and non-contact infrared thermometer has specific instructions for use and additional information that the user of the device should follow to increase accuracy.

Temperature measurements can also be affected by several factors including, but not limited to, the person's clothing (including hats and scarves), the testing location and device preparation, the training of the person handling the device, and environmental factors such as room temperature and relative humidity. 

Regulation of Non-contact Temperature Assessment Devices  

To help expand the availability of telethermographic systems (also known as thermal imaging systems) and clinical electronic thermometers (including non-contact infrared thermometers) during the COVID-19 pandemic, the FDA issued the following guidances:

For assistance with technical and regulatory requirements for medical devices, please see:


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