BBC Focus - 04.2020_

Previously, we’ve seen multiple waves,

and could – if we didn’t take action –

also expect to see multiple waves of

COVID-19. We’re in the first wave now.

If infection rates were to fall over the

summer, due to seasonal factors or to

our control efforts, we could expect

to see one next winter, while there’s

still a substantial proportion of people

who aren’t immune. The government is

taking that possibility into account and

is planning for control measures.

WHAT CAN WE LEARN FROM PREVIOUS
CORONAVIRUSES?
My first employment was working on
a coronavirus back in the 1980s, and
we knew of two then, OC43 and 229E.
It’s probable that tens of thousands of
years ago, they first emerged from bats,
or other animals, into humans as novel,

and possibly dangerous, viruses that

gradually spread across the world with

population movements, mutating and

becoming tailored to co-existence with

us. They tell us quite a lot that will be

important as we move forward with

controlling or eradicating COVID-19.

Those two viruses haven’t changed

much, and yet people get colds every

winter caused by them. We think about

15 to 20 per cent of colds are caused

by coronaviruses. There’s not been

sufficient work done on them to fully

understand them, as funders don’t

spend a lot of money on viruses that

don’t cause much by way of disease. We

know that influenza keeps circulating

because it keeps mutating and avoids

our existing immunity – we say they

undergo ‘genetic drift’. But if a virus

is to keep circulating, like the older

coronaviruses,andisn’tchanging

much,there’sonlyreallyoneother

explanationforthatasfarasI can see:

theimmunitytheyinduceis probably

fairlyshort-lived.Somevirusinfections

providealmostlife-longimmunity, but

forothers,it’snotsolong.Forexample,

wecancatchnorovirusoneyear,then

a yearortwolaterwecangetit again.

ShouldthatbethecaseforCOVID-19, it

wouldhaveimportantimplications for

itsepidemiologyandcontrol.

WHATISLIKELYTOHAPPENNEXT?

Atthemomentwe’reallnon-immune,

butaspeoplecatchandrecoverfrom

COVID-19,weexpectthevastmajority

tobecomeimmune.It is likelythat

morepeoplewillbecomeimmune

duringsubsequentwavesandwecan

expectthevirustoreturnuntil,at

currentestimates, 60 percentofthe

population have acquired immunity.

At this point, we’ll have established

‘herd immunity’, where there aren’t

enough non-immune people around for

the virus to cause any more epidemic

peaks. In fact, at this point, the virus is

liable to become endemic, and we might

see small seasonal peaks of infection

among members of the population who

are non-immune, or who have been

born since the earlier waves. If that

does happen, we’ll be dependent on the

development, testing, introduction and

roll-out of an effective vaccine to stop

the virus circulating. That, of course,

will need to be achieved globally, if we

are to eradicate this virus and prevent it

from posing an ongoing threat.

by DR MIKE SKINNER

Mike is a virologist based at Imperial College

London. Interviewed by BBC Science Focus

commissioning editor Jason Goodyer.

DISCOVERIES

Police cordon tape during

the COVID-19 lockdown at

Levante beach in Benidorm