Airports And Coronavirus: Screening For Safety?

The effectiveness of airport screening for COVID-19 has been a topic of debate since the early days of the pandemic. While some countries implemented airport screenings for arriving passengers, the impact of these measures on curbing the spread of the virus has been questioned. In the United States, the Centers for Disease Control and Prevention (CDC) instituted screening programs at select airports to identify travellers with COVID-19 symptoms or exposure history. However, by September 2020, the CDC decided to end these screenings due to their limited effectiveness in identifying infected individuals.

The screenings, which took place at 15 US airports, included temperature checks and health questionnaires for incoming international travellers. Despite these efforts, the CDC reported that only 0.001% of screened travellers tested positive for COVID-19. The low yield of these screenings led the CDC to shift its focus towards more effective mitigation strategies, such as health education, enhanced training for transportation employees, and voluntary electronic data collection.

While airport screenings may have played a role in raising awareness and discouraging ill travellers from travelling, their overall impact on preventing the spread of COVID-19 was limited. This is partly due to the nature of the virus, which can be transmitted by asymptomatic or presymptomatic individuals, as well as the challenges of accurately identifying infected individuals through temperature and symptom checks alone.

Screening methods: temperature checks and health questionnaires

Screening methods at airports have been an important topic of discussion during the COVID-19 pandemic. While these methods are intended to prevent the spread of the virus, their effectiveness has been questioned. Two common screening methods employed by airports are temperature checks and health questionnaires.

Temperature checks are typically conducted using thermal cameras or infrared thermometers held a few inches from an individual's forehead. This contactless approach allows for mass screening of passengers without causing delays. Some airlines and airports, such as Air Canada and Paine Field in Washington State, have already implemented temperature screening. However, the effectiveness of temperature checks has been debated. Critics argue that individuals can have the coronavirus without exhibiting a fever, and a study published in the journal Nature found that carriers may be most contagious before becoming symptomatic. Additionally, thermal scanners and thermometers can produce false positives and negatives, and individuals can lower their temperature temporarily with fever-suppressing drugs.

Health questionnaires aim to identify individuals with COVID-19 symptoms or those who have been in close contact with infected people. These questionnaires are often required to be filled out by passengers during the check-in process or upon arrival at their destination. Questions may include inquiries about recent travel history, exposure to infected individuals, and the presence of symptoms such as fever, cough, or difficulty breathing. While health questionnaires are a useful tool, they rely on individuals' honesty and accuracy in reporting their health status and travel history.

Despite the limitations of temperature checks and health questionnaires, they can still play a role in the overall public health response to the pandemic. For example, health questionnaires can help gather contact information for potential tracing efforts. Additionally, screening methods may provide some reassurance to travellers and help identify individuals who require further medical examination or testing. However, it is important to recognise that these screening methods are not foolproof and should be complemented with other preventive measures, such as wearing face masks, using hand sanitiser, and adhering to social distancing guidelines.

Screening ineffectiveness: asymptomatic cases and mild symptoms

The effectiveness of airport screening for COVID-19 has been a topic of much discussion and debate. While some countries implemented airport screening measures to identify infected travellers, the effectiveness of these screenings has been questioned, especially in the case of asymptomatic and mild symptom carriers.

Asymptomatic cases refer to individuals who are infected with COVID-19 but do not exhibit any symptoms. This poses a significant challenge to containment efforts as these individuals can unknowingly spread the virus to others. Mild symptoms, on the other hand, may be difficult to detect or can be mistaken for other common illnesses.

In the United States, the Centers for Disease Control and Prevention (CDC) implemented a screening program for air passengers arriving from certain countries with high rates of COVID-19 transmission. The program included measures such as temperature checks and health questionnaires. However, the CDC later ended this screening program due to its "limited effectiveness". The CDC acknowledged that symptom-based screening has limited effectiveness because individuals with COVID-19 may not show any symptoms or only experience mild symptoms at the time of screening.

Mathematical models and studies have supported the notion that symptom-based screening at airports is largely ineffective in detecting infected travellers. The reasons for this ineffectiveness include the relatively long incubation period of COVID-19, the wide range of symptom severity, the presence of afebrile cases, and nonspecific symptoms that overlap with other common illnesses. Additionally, travellers may deny symptoms or take medication to suppress symptoms, further reducing the effectiveness of screenings.

As an alternative to traditional screening methods, researchers have explored the use of trained dogs to detect COVID-19 cases, including asymptomatic individuals. The dogs were able to successfully identify positive cases by smelling sweat, saliva, and urine samples, with accuracy rates ranging from 82% to 95%. This detection method could provide a quick and non-invasive way to identify infected individuals within large groups, such as at airports or mass gatherings.

While airport screenings may have limited effectiveness in detecting asymptomatic cases and mild symptoms, public health authorities have shifted their focus to other strategies such as enhancing communication with travellers, promoting recommended preventive measures, and encouraging pre-departure and post-arrival testing to reduce the risk of COVID-19 transmission during travel.

Screening alternatives: health education, illness response, voluntary data collection

Screening alternatives such as health education, illness response, and voluntary data collection can be effective tools in managing the spread of COVID-19.

Health education plays a crucial role in empowering individuals to take preventive measures and promote recommended practices. Health Education England, for instance, offers a free e-learning programme that provides essential guidance from the NHS, UK Government, WHO, and BMJ. It covers topics such as personal protective equipment (PPE), infection prevention, and control measures.

Illness response mechanisms are also vital. After the screening programme ended in September 2020, the focus shifted to reinforcing mechanisms to refer overtly ill travellers to the CDC and enhancing public health response capacity at ports of entry.

Voluntary data collection mechanisms, such as online surveys and questionnaires, can be used to gather clinical data from the general public to detect COVID-19 symptoms. This approach respects data privacy and security while providing valuable insights for advanced identification and evaluation of COVID-19 cases.

Furthermore, to reduce the risk of COVID-19 transmission during travel, additional precautions are recommended for travellers with higher exposure risk. These include post-arrival testing, avoiding contact with high-risk individuals, and adhering to jurisdictional public health guidelines, such as self-quarantine.

Screening in China: 20 airports, questionnaires, temperature checks

In response to the emergence of the coronavirus in Wuhan, China, the US government issued a "Do Not Travel" advisory, urging citizens not to travel to China due to the ongoing epidemic. By mid-January 2020, the Centers for Disease Control and Prevention, in collaboration with state and local public health authorities, implemented screening protocols at three US airports for passengers arriving from Wuhan, China. These entry points were later expanded to 20 airports across the US. As part of the screening process, passengers were required to complete a short questionnaire about their travel history, symptoms, and contact information. Additionally, CDC employees conducted temperature checks using handheld scanners and assessed travellers for coughing or breathing difficulties.

The screening protocols aimed to identify travellers with COVID-19 symptoms or those who had been exposed to the virus. Suspected cases were referred for additional public health assessment, and if necessary, sent to a local healthcare facility for medical evaluation. While these measures helped identify some cases, they had limited effectiveness due to the challenges of asymptomatic carriers and the long incubation period of the virus.

To enhance the effectiveness of screening efforts, the CDC shifted its strategy to focus on more targeted mitigation efforts. This included prioritising health education, improving illness response at airports, implementing voluntary electronic data collection, and enhancing training for transportation employees.

The screening procedures at US airports for international travellers played a crucial role in identifying and managing potential COVID-19 cases. However, the dynamic nature of the virus and its transmission presented ongoing challenges, requiring a flexible and adaptive approach to infection control.

Screening history: 14th-century Venice, 20th-century San Francisco

Screening for diseases at ports of entry has been a strategy used for centuries to prevent or slow the spread of infectious diseases. Here is a brief history of screening measures in the 14th-century Venetian plague and the 20th-century San Francisco plague:

14th-Century Venice:

During the 14th century, Venice was ravaged by the Black Death or bubonic plague, which is caused by the bacteria Yersinia pestis. This plague had a significant impact on the city, and the Venetian people tried to prevent its spread through surveillance and quarantine measures. The Lazzaretto Vecchio and the Lazzaretto Nuovo, two burial sites from the 14th to 16th centuries, played central roles in these preventive efforts.

At the time, people had a limited understanding of the medical and scientific reasons for the plague. However, the implementation of quarantine measures and the isolation of affected areas were crucial in controlling the spread. High-throughput, multiplexed real-time PCR detection methods have been used to identify Yersinia pestis DNA in dental pulp specimens collected from medieval Venetian burial sites, providing evidence of successive plague epidemics in the city.

20th-Century San Francisco:

In the early 20th century, San Francisco faced an epidemic of bubonic plague, centred on the city's Chinatown. The epidemic was recognised by medical authorities in March 1900, but its existence was denied by California's Republican Governor, Henry Gage, due to business and economic concerns. Federal authorities, including Joseph J. Kinyoun, the chief quarantine officer of the Marine Hospital Service (MHS) in San Francisco, worked to prove the presence of the plague and isolated the affected area.

Despite the efforts of federal authorities, the denial and suppression by Governor Gage hindered the initial response to the outbreak. He publicly denied the existence of any pestilent outbreak, fearing economic damage to the city and state. Supportive newspapers echoed his denials, and a defamation campaign was directed at Kinyoun. The clash between Gage and federal authorities intensified, and Kinyoun faced opposition from the state and local officials, the press, and even the president of the United States.

However, the federal government persisted, and a commission of respected medical scholars examined the outbreak, conclusively determining the presence of bubonic plague. This led to the implementation of public health measures by the new governor, George Pardee, and the epidemic was eventually stopped in 1904. The response included rat extermination efforts, with approximately $2 million spent between 1907 and 1911 to control one of the disease's vectors.

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