The Economist USA 03.28.2020

70 Science & technology The EconomistMarch 28th 2020

2 erairlines arewillingto continuetobe

boundtosomethingratherdifferentfrom

what theyoriginally thought theywere

signingupto.

Ultimately,theoutcomeofcovid-19for

theclimatewilldependontwounknowns.

One is how long the pandemic lasts—

something over which politicians have

somecontrol,butcertainlynotasmuchas

theywouldlike.Theotherishowgovern-

mentschoosetopulltheireconomiesout

oftheholenowbeingcreated,whichisen-

tirelya matterofpolitics.

The lazyway,theeasy way,to boost

countries’economiesinresponsetothevi-

ruswould beforgovernments tothrow

moneyatestablishedversionsof bigin-

dustrieslike energy, transport and con-

struction. They could, though, if they

chosetodoso,spendthecashinsteadon

encouragingclimate-friendlyversionsof

these industries: more solar energy (or

even,heavenforfend,nuclearpower)in-

steadofbungstooilandgas;morebatteries

forcars,andmoneyforresearchintohy-

drogen-poweredfuelcells;cashprizesfor

waysofmakingsteelandcementwithout

releasingCO 2 ; andsoon.

FatihBirol, headoftheInternational

EnergyAgency,anintergovernmentalor-

ganisationthatoperatesundertheaegisof

theoecd, hasalreadyputoutapleafor

greenstimuliof this sort.Similarcalls,

though,weremadein 2008 and2009.They

fellondeafears.Perhapsthistimearound

it willbedifferent. 7

S

ticking a thermometerinto an arm-

pit, mouth, ear or other body cavity is

the most accurate way to take someone’s

temperature. Understandably, though, this

cannot be done at airports or checkpoints

set up elsewhere to screen the masses for

feverish victims of covid-19. So, in a bid to

detect the warmth produced by a fever

without touching any bodies, officials have

opted for alternatives.

The hand-held “thermometer guns”

now ubiquitous in China, among other

places, are one option. These instruments,

known technically as spot pyrometers, use

a device called a bolometer to estimate an

object’s temperature. A bolometer’s electri-

cal resistance depends on how hot it is.

That, in turn, depends on the amount of in-

frared radiation falling on it from whatever

it is pointing at.

Spot pyrometers are used widely in in-

dustry to check equipment for signs of

overheating, but the infrared signals they

rely on can be muddled by dust, moisture,

smoke, a change in ambient temperature, a

smudge on the device’s lens or even by ra-

dio signals. Beyond all this, an official

checking a stream of foreheads may, for

reasons of personal safety, be reluctant to

hold the gun close enough to obtain an ac-

curate reading.

An alternative technology, the thermal

camera, is costlier. But it can operate from

farther away. Instead of a single bolometer,

it has an array of them. These form the pix-

els which generate the camera’s image,

thus building up a heat map of whatever

that camera is looking at.

One popular thermal camera, the A320,

made by flir Systems, an American firm,

can detect variations in radiation which

correspond to temperature differences

within an image of just 0.02°C. But this

merely shows whether one part of the ob-

ject being examined is warmer or cooler

than another. When measuring the object’s

actual temperature, the A320 is accurate

only to about 2°C, says Giovanni Scaglia,

flir’s head of sales in Italy. For a single

reading, this is enough to mistake normal

body temperature for a raging fever. In

practice, however, the camera’s software

looks for deviations from the average tem-

perature of passers-by. Those noticeably

hotter than their fellows can then be select-

ed for closer investigation.

Identifying individuals who are infect-

ed is important, in order to stop them pass-

ing the virus on. But temperature data can

also be used to track the epidemic as it

spreads. This is the goal of Kinsa Health, a

firm in San Francisco that has sold or do-

nated more than 1m smartphone-connect-

ed thermometers to households in Ameri-

ca. The phones these thermometers are

linked to carry an app that transmits back

to base each body-temperature recording

which its user makes. The app can then

give simple medical advice (for example,

based on age, sex and so on, does a user

with a particular temperature need to see a

doctor or not?) The app also provides epi-

demic information about the neighbour-

hood, including such things as how badly

local schools are affected.

Using its thermometers and apps, Kinsa

has built up a trove of data on past fevers in

America. Besides being good for public

health, this information has commercial

value. One American pharmacy chain pays

Kinsa for fever data in order to avoid partic-

ular stores selling out of things the feverish

may wish to purchase.

In the past, Kinsa’s focus has been on in-

fluenza. But now the fear is that any elevat-

ed body temperature is the result of co-

vid-19. On March 18th the firm began

posting relevant data, duly anonymised,

but more or less in real time, on a website

called Health Weather. In contrast to this

“nowcasting”, a government site called Flu-

View, which is run by the Centres for Dis-

ease Control and Prevention, relies on

sources like hospitals to provide it with

data, and tends to lag an epidemic by about

two weeks.

Once a fever kicks in, people tend to

take their temperature frequently. Kinsa

therefore knows a lot about how an epi-

demic is progressing, and how severe it is,

in lots of different places around America.

In the past, this has enabled it to make ac-

curate forecasts of disease burden down to

the level of individual zip codes. According

to Nirav Shah of Stanford University, who

advises the firm, such forecasts can look up

to 20 weeks into the future for influenza.

Covid-19 is not influenza, of course, and

presumably has different patterns of

spread. But even before these have been

worked out properly, data from Kinsa’s re-

mote thermometers are flagging up useful

warnings. As The Economistwent to press,

atypically high numbers of fevers had

popped up in much of peninsular Florida.

Time, then, for Floridians to get off the

beaches and start keeping their distance

from one another. 7

Taking people’s temperatures can help to fight the spread of the coronavirus

Detecting elevated body temperatures

And now here is the fever forecast

Bolometers to the fore