Chinese authorities are using infrared thermometers to screen people for diseases because these devices have become synonymous with attempts to contain the deadly epidemic.

These devices are accurate in the clinical environment used by professionals. In times of crisis, their accuracy is questionable. Image source... Carter Johnston for The New York Times

It has become an iconic image of the coronavirus outbreak in China: a masked official pointed a small white pistol at the traveler's forehead.

For weeks, this ominous-looking device has been deployed at checkpoints across China-toll booths, apartment buildings, hotels, grocery stores, railway stations-and government officials and ordinary citizens are screening people for fever. Prevent the spread of the deadly coronavirus.

Sometimes described as a "thermometer gun", the device is equipped with an infrared sensor that can quickly measure the surface temperature without any contact with the human skin. In recent years, it has become an important tool for countries to fight to contain the virus outbreak. In the early 2000s, it was widely used to slow the spread of SARS in China and to contain the Ebola epidemic in West Africa ten years later.

But according to medical officials and infrared equipment experts, although the thermometer has powerful sensing technology, it turned out to be an ineffective defense mechanism. Like the ubiquitous surgical masks in China, thermometer guns are often unreliable outside of strictly controlled medical environments.

Thermometers determine the temperature by measuring the heat radiated from the surface of the human body. However, under normal circumstances, the person using the tools will not bring them close to the subject's forehead, resulting in abnormally low temperature readings, or hold them too close and obtain high readings. In some environments, the measurement may be inaccurate, such as a dusty roadside, or when someone is taking medication to suppress fever.

"As we all know, these devices are not accurate or reliable," said Dr. James Lawler, a medical expert at the Center for Global Health and Safety at the University of Nebraska. "Frankly, some of them are for acting."

During the Ebola outbreak, Dr. Lawler was often tested by infrared thermometers outside the hospital or at roadside checkpoints while traveling in West Africa. It turns out that he died of hypothermia.

"My body temperature is usually 35 degrees Celsius or lower, which is starting to be incompatible with life," said Dr. Lawler. "So I'm not sure those are accurate."

In theory, thermometers and more sophisticated cameras can also measure a person's body temperature, allowing local officials to quickly determine who may have a fever, and then pull these people aside for further testing. So far, tens of thousands of people have been infected with the coronavirus, and the death toll this week exceeded 1,000. Last month, the World Health Organization stated that temperature screening can reduce the "risk of importation."

But on social media in China, people passing through checkpoints complained that thermometers would produce unrealistically low readings in some cases, and artificially high readings in other cases, such as in a hot car for travelers. When testing.

"You know the temperature gun is inaccurate," a netizen wrote after reading a guard's reading on the Chinese social media service Weibo. "I know that the temperature gun is inaccurate. He also knows that the temperature gun is inaccurate. But no one said anything because it is part of the process. This formalism!"

Just because the infrared tool shows that a person's temperature is high does not mean that the person is sick, let alone carrying a virus.

"They may have been exercising, they may be taking certain medications," said Jim Seffrin, an infrared device expert at the Infraspection Institute in New Jersey. "A person trying to catch a plane at a late airport-they may have ran into the lobby."

The growing demand for thermometer guns and infrared cameras that can detect fever has caused shortages around the world, from Wuhan, the epicenter of the outbreak, to a small supplier in Texas.

Many Chinese companies produce thermometer guns, which have become more expensive as the demand from the government and private customers (such as schools and factories) increases.

Alicn Medical (Shenzhen) is a manufacturer in Shenzhen, China, which produces 2.5 million thermometer guns every year. It is one of the few companies in China that can achieve this level of production, said its general manager Mo Yingchun. Nevertheless, the cost of raw materials has soared, and many workers cannot escape China’s epidemic control efforts to come to work, which means that the company is not producing at full capacity.

"Even governments are competing with each other for products," Mr. Mo said, noting that prices have risen to three to five times the usual level. "The local government must first ensure its own needs."

He added that under normal circumstances, the company's thermometer is used indoors to check babies. "The thermometer gun is only used for rapid screening and is not as accurate as traditional thermometers," Mr. Mo said. "This is a small industry. If it weren't for the epidemic, it would not be the focus of people's attention."

Thousands of miles away from the epicenter of the epidemic, a small technology supplier in Beaumont, Texas, also felt the squeeze in demand. The company called Infrared Cameras produces high-tech imaging equipment and infrared thermometers, each priced at $25.

According to its CEO Gary Strahan (Gary Strahan), in a normal month, the company will sell about 100 infrared cameras. Since January, the company has sold more than 1,000 units to schools, cruise ships, factories, offices, hospitals, and theaters in countries such as China and South Korea.

Mr. Strahan said that he works every day from 4 am to 10 pm to keep up with orders.

"This is the most irresistible thing I have to face in my life," he said. "Someone came to us directly and said:'Can you provide 1,000 cameras? Can you provide 2,000 cameras?'"

Mr. Strahan, who has been selling infrared cameras since the 1990s, said that the company's cameras and thermometer guns have an error range of 0.1 to 0.2 degrees Celsius. But many products on the market are not very reliable.

During past outbreaks, some checkpoints used cameras or thermometer guns designed for industrial use, such as measuring the temperature of vehicles, rather than finely calibrated medical tools.

"If you want to use this technology, you must be equipped with the right equipment," said Mr. Seffrin of the Inspection Institute. "What we saw during the SARS outbreak was that people quickly picked up industrial instruments."

Even a perfectly accurate temperature sensor may not be able to capture everyone who carries the coronavirus. According to the New England Journal of Medicine, it may take several days for an infected person to develop a fever. Travelers who already have a fever may take Tylenol to suppress symptoms, sometimes deliberately deceiving the authorities. In China’s Qinghai Province, the police are investigating a man suspected of passing a checkpoint while covering up his illness.

Nevertheless, Mr. Strahan said that he hopes his company can help slow the spread of the virus, even if temperature screening is unlikely to completely prevent the outbreak.

He said: "Because many of the systems sold out there are inaccurate, people will be missed and the infection will spread." "This is a very real situation and I feel like I am in it."

This is indeed the case on Thursday morning: In the company's office in Beaumont, Mr. Strahan's team is packing 300 thermometer guns into boxes and shipping them all to China.