Airport Fever Checks: Are They Effective?

In the wake of the COVID-19 pandemic, South Korea introduced a three-layered airport fever check at Incheon International Airport. This procedure involves checking the temperature of departing passengers with thermal cameras, then using more thermal cameras in the departure area, and finally measuring their temperatures at the boarding gate with a non-contact thermometer. This comes as dozens of countries have limited arrivals from South Korea. However, the effectiveness of fever screening at airports has been questioned by experts, who argue that it is mostly a waste of time and that there are a lot of false positives.

Airports use thermal cameras to check for fever

Thermal cameras are used to screen large numbers of people quickly and efficiently. They work by measuring the heat that a person emits from a distance of 0.3 to 2 meters away, and displaying this as a heatmap. This method is much faster than using a forehead thermometer, and it also helps to reduce close contact between screeners and travellers.

In Hawaii, for example, thermal cameras were installed at five airports that receive transpacific flights. National Guardsmen monitor the camera feed in real time and anyone with a temperature above 100.4 degrees Fahrenheit is flagged for an additional health evaluation.

However, the effectiveness of temperature screening as a way to detect COVID-19 has been questioned, as not all COVID patients display a fever. Nevertheless, an expert from the East-West Center cited a study from Taiwan which found that thermal screening at airports can identify up to one-third of COVID-positive flyers.

The use of thermal cameras in airports has also raised concerns about privacy and civil liberties, especially when paired with facial recognition technology.

IR thermometers have a high false-positive rate

Another factor that affects the accuracy of IR thermometers is emissivity. Emissivity is the efficiency at which an object emits thermal energy, and different materials have different emissivity values. While some IR thermometers have adjustable emissivity settings, others have fixed values that may not be suitable for all surfaces. If the emissivity setting is incorrect, it can result in significant inaccuracies. For instance, measuring the temperature of a stainless steel grill lid on a warm spring day with the wrong emissivity setting can result in a reading that is off by a hundred degrees or more.

Furthermore, IR thermometers measure surface temperatures, and their readings can be affected by what is beneath or beyond the surface being measured. For instance, when measuring the temperature of a grill, the thermometer may pick up the heat from the flames or coals below the grates instead of the surface temperature of the grill itself. Similarly, when measuring the temperature of a liquid, the reading may be affected by the temperature of the container holding the liquid.

To minimize false positives, it is important to follow proper techniques when using IR thermometers. This includes ensuring that the thermometer is perpendicular to the surface being measured and that there are no obstructions such as glass, water, smoke, or steam between the thermometer and the surface. Additionally, it is crucial to understand the limitations of IR thermometers and treat their readings as relative rather than absolute. Comparing readings from multiple IR thermometers or using other types of thermometers, such as probe thermometers, can also help improve accuracy and reduce false positives.

Fever screening is unlikely to prevent a pandemic

Fever screening is a common measure implemented at airports to detect febrile international passengers and prevent the spread of infectious diseases. While it may provide confidence to travellers and help in building trust, fever screening alone is unlikely to prevent a pandemic due to various limitations and factors.

Firstly, fever screening has limited effectiveness in identifying infected individuals. During the 2009 influenza pandemic, fever screening at Narita International Airport in Japan detected only 22.2% of confirmed H1N1 cases, with 55.6% of these cases under antipyretic medication. Similarly, in Singapore, only 12.9% of the first 116 H1N1-infected individuals with a history of international travel were identified through airport screening. This low sensitivity of fever screening is attributed to the presence of asymptomatic cases and the short incubation period of the virus, allowing transmission before the onset of symptoms.

Secondly, the technology used for fever screening, such as infrared thermoscanners, has limitations. The sensitivity of infrared thermoscanners in detecting hyperthermia ranged from 50.8% to 70.4%, with a positive predictive value as low as 37.3%. Additionally, these devices measure surface temperature, which may not accurately reflect internal body temperature and can be influenced by factors like sunburn or hot environments.

Thirdly, fever is a non-specific symptom and may not be present in all infected individuals. In the case of COVID-19, it is estimated that 35% of infections are asymptomatic, and individuals may be symptomatic without having a fever. Thus, fever screening alone may miss a significant portion of infected individuals.

Furthermore, fever screening may provide a false sense of security, leading to a reduction in adherence to other preventive measures such as social distancing and handwashing, which have a more evidence-based impact on preventing disease spread. Additionally, fever screening raises privacy concerns related to physiological surveillance and data collection, and there is a risk of stigmatization for those perceived as a risk.

In conclusion, while fever screening may be a useful component of a comprehensive approach to infectious disease control, it is unlikely to prevent a pandemic on its own. A more effective strategy may be to focus on community-based measures such as early identification and treatment of cases, social distancing, infection control, and improving ventilation, along with effective communication with travellers and clinicians.

Temperature checks were introduced in some countries during the Ebola outbreak

During the 2014 Ebola outbreak, some countries introduced temperature checks at their airports. This was an attempt to prevent the virus from being brought into the country by international travellers.

In the US, five airports were ordered to start screening travellers for Ebola. These were New York's John F. Kennedy International Airport, Washington-Dulles, Newark, Chicago-O'Hare, and Hartsfield in Atlanta. Together, these airports handled 94% of US-bound flights from the Ebola-affected countries. The US Centers for Disease Control and Prevention (CDC) stated that travellers would have their temperature taken, be observed for symptoms of Ebola, and be asked questions to determine their risk of the disease.

Canada also stepped up border screening at six airports: Montreal, Toronto, Vancouver, Halifax, Ottawa, and Calgary. Travellers from West Africa would undergo temperature checks and health assessments by quarantine officers.

Despite these measures, experts have questioned the effectiveness of airport temperature screening. Ran Balicer, an infectious diseases expert, noted that the time between contracting Ebola and developing a fever could be as long as 21 days, reducing the likelihood of detecting potential patients. Lawrence Gostin, a professor of global health law, agreed that screening would identify only a few Ebola cases at best and could divert attention and resources from other important areas such as public health and hospital preparedness.

Fever screening has been used in Asia to detect Bird Flu

In Asia, fever screening has been used as a measure to detect bird flu in humans, particularly after the SARS outbreak. For example, Hong Kong kept its elevated temperature screening cameras in airports after the SARS pandemic, which allowed them to be prepared for the COVID-19 pandemic.

Fever screening systems typically consist of four main components: a combined thermal imager and optical camera, a blackbody for calibration, a video recording device or network video recorder, and an additional display screen. These systems can help identify individuals with elevated temperatures, one of the symptoms of bird flu, and prevent them from travelling by plane.

It is important to note that bird flu is rare in humans, and there is no clear evidence that it can be transmitted from human to human. However, fever screening in airports can be a useful tool to detect potential cases and prevent the spread of the disease.

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