Why Screening for Ebola By Taking Temperature CAN’T Work

Screening With a Thermometer Is Guaranteed to Fail …

The Los Angeles Times explains why trying to screen Ebola victims by taking their temperature won’t work:

A person could pass body temperature checks performed at the airports by taking ibuprofen or any common analgesic. And prospective passengers have much to fear from identifying themselves as sick, said Kim Beer, a resident of Freetown, the capital of Sierra Leone, who is working to get medical supplies into the country to cope with Ebola.

“It is highly unlikely that someone would acknowledge having a fever, or simply feeling unwell,” Beer said via email. “Not only will they probably not get on the flight — they may even be taken to/required to go to a ‘holding facility’ where they would have to stay for days until it is confirmed that it is not caused by Ebola. That is just about the last place one would want to go.


The potential disincentive for passengers to reveal their own symptoms was echoed by Sheka Forna, a dual citizen of Sierra Leone and Britain who manages a communications firm in Freetown. Forna said he considered it “very possible” that people with fever would medicate themselves to appear asymptomatic.

It would be perilous to admit even nonspecific symptoms at the airport, Forna said in a telephone interview. “You’d be confined to wards with people with full-blown disease.”

In other words, Ebola carriers who fail to take something to lower their temperature are signing their own death warrants.   The incentive to cheat is so high – life or death – that testing through temperature alone is totally worthless.

In addition, even the Centers for Disease Control admits that thermal scanners often fail.  As the Guardian reports:

Checking body temperature isn’t a sure-fire way to find individuals infected with Ebola. People can carry the virus for up to three weeks before showing symptoms, and are not contagious during that period. The patient in the US case, Thomas Eric Duncan, was reportedly asymptomatic when he travelled from Liberia to Dallas.

In a guidance paper produced by the Centers for Disease Control and Prevention for airport and public health officials, the agency lists what it sees as problems with the devices, including cost, lack of precision, need for frequent calibration and maintenance and training requirements. Testing efficacy to judge the scanners write large is difficult because of the many and changing models available.

While such scanners can be good at ruling out people without fevers, the CDC said, they have a wide and varying range of efficacy at finding people with fevers depending on environmental conditions and even the age of the person being scanned. The FDA approved the devices for use only with more conventional methods of taking someone’s temperature, such as a mercury thermometer or color-changing strips.

“Policy makers may feel some pressure to use [non-contact infrared thermometers],” said French researchers at the Institut de Veille Sanitaire. “But the decision making process should not ignore the poor scientific evidence on NCIT’s efficacy to delay the introduction of a novel influenza strain.”

“The psychological reassuring effect on the public can influence the decision to implement such screening, as was the case in Singapore and Canada,” said the same study from Institut de Veille Sanitaire. “But these countries also recognised that the public may lose confidence in this measure if an undetected case had entered the country and generated secondary cases.”

In other words, thermal scanners are really just for show … and the public is going to catch on and become disillusioned pretty quickly.

Update: MarketWatch confirms:

Is the U.S. Ebola screening effort really just a public-relations ploy?

Health officials say beefed-up defenses in five U.S. airports mean they will screen 94% of passengers flying in from Ebola-hit countries. But a check of airlines schedules shows that even if that figure is correct, a significant number of flights will bypass that extra security.

Dr. Joseph McCormick, professor at the University of Texas School of Public Health and former CDC official specializing in viral diseases, says the efforts seem to be the result of public pressure.

I think that the screening program is, to some degree, a response to the media,” said McCormick, who once led a team investigating a 1979 Ebola outbreak in the Sudan.

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  • clarioncaller

    Why don’t the doctor’s who are receiving these incoming plague-carriers ask them to turn their heads and cough?

  • jadan

    So, there is no quick, accurate, and cheap test for the virus? That would solve the problem if there were technology that would identity Ebola like a diabetic checks blood sugar.

  • kimyo

    Ebola research: Fever not a surefire sign of infection

    So long as an individual’s temperature does not exceed 101.5 degrees and there are no visible symptoms of Ebola, health authorities say it should be assumed the person is not infectious.

    Yet the largest study of the current outbreak found that in nearly 13% of “confirmed and probable” cases in Liberia, Sierra Leone, Guinea and elsewhere, those infected did not have fevers.

    The study, sponsored by the World Health Organization and published online late last month by the New England Journal of Medicine, analyzed data on 3,343 confirmed and 667 probable cases of Ebola.

    Dr. Nick Zwinkels, a Dutch physician, last month closed a hospital he had been running with a colleague in central Sierra Leone after five nursing aides contracted Ebola — possibly from unprotected contact with three patients who were not promptly diagnosed with the virus.

    Four of the nursing aides died, as did all three of the patients belatedly found to have Ebola.

    Interviewed by email, Zwinkels said that hospital staff members took the temperature of one of the doomed patients four times a day for three consecutive days, and the patient never showed a fever. The readings were taken by a digital thermometer placed in the armpit, he said.

    Based on what his staff observed, Zwinkels wrote, “it seems that only measuring the temperature as a form of triage is insufficient.”

    He added: “It seems that Ebola can present without fever especially in the first phase.”