One case per 85,000 travellers, at $57 million

In January 2020, CDC began screening air passengers arriving from countries
with widespread SARS-CoV-2 transmission — starting on **17 January at Los
Angeles, San Francisco and John F. Kennedy**, the three airports taking the
most passengers from Wuhan.

What it caught

One case per roughly 85,000 travellers screened.

What it cost

About $57 million transferred to the Department of Homeland Security, plus
all CDC personnel and contractor costs, equipment, travel, and housing for
quarantined travellers. **At its peak on 20 March, the designated airports
were staffed by approximately 750 screeners** plus supporting personnel.

Why it could not work

The screening was three steps: **Customs and Border Protection identified
travellers who had been in a specified country in the previous 14 days**; then
**observation for signs of illness, a non-contact infrared temperature check
(fever ≥100.4°F / 38°C), a questionnaire** about fever, cough and difficulty
breathing in the previous 24 hours or exposure in the previous 14 days, **and
collection of US contact details**; then referral of the ill to an on-site
medical officer.

Of the 298 referred, 278 (93.3%) were for symptoms — most often **cough
(73%)**, self-reported fever (41%), measured fever (17%) and difficulty
breathing (13%). Sixteen had been in Hubei Province; four reported contact
with a case.

The conclusion is stated plainly:

**Because SARS-CoV-2 infection and transmission can occur in the absence of
symptoms and because the symptoms of COVID-19 are nonspecific, symptom-based
screening programs are ineffective for case detection.**

A thermometer at a border catches people with a fever. It does not catch
people who are infectious and feel fine, and it stops a great many people who
have an ordinary cough.

The part that would have been worth having

The other purpose of screening was to **collect contact information to pass to
state health departments** — which is about contact tracing rather than
detection, and might have justified a great deal on its own.

It did not work either:

CDC sent states contact information for about 68% of screened travellers —
the shortfall from records processed more than 12 days after arrival,
insufficient data, and six states that opted out because of competing
response priorities.

The 98.1% against 22% is the finding worth keeping: the data was only good
when a person collected it by hand, at an airport, one traveller at a time.

What replaced it

Screening ended on 14 September 2020. Effort moved to **communicating with
travellers about preventive measures**, **reinforcing referral of overtly ill
travellers**, and **strengthening public health response capacity at ports of
entry.**

And the recommendation the contact-data numbers argue for: **more efficient
collection of contact information before arrival, transferred to health
departments in real time** — plus **health attestations, predeparture and
postarrival testing, and a period of limited movement after higher-risk
travel.**

Testing after arrival finds what a temperature check cannot. Contact details
gathered before departure cost nobody 750 staff.

Source: Centers for Disease Control and Prevention, MMWR.