Social distancing is a good place to start
Source article: STAT
Tel Aviv-Savidor Central railway station, March 17, 7:30 p.m. PHOTO: NATHALIE ANDRIJASEVIC |
He is absolutely right on the first point. The U.S. has done fewer tests per capita so far than almost any rich country in the world. And many critical details of the epidemiology — including the absolute number of cases, the role of children in transmission, the role of presymptomatic transmission, and the risk of dying from infection with SARS-CoV-2 — remain uncertain.
On
the second point, I would say that his article did what contrarian writing
should do: started a discussion. We spoke by phone on Tuesday, not long after
his article appeared, and found that we had more in common than it appeared
when I first read it.
So without trying to characterize Ioannidis’
view, I will state a strongly held view of my own: We know enough to act;
indeed, there is an imperative to act strongly and swiftly. It is true that we
can’t be sure either how many infections there have been in any population or
the risk of needing intensive care or the case fatality rate. These
uncertainties are two sides of the same coin. Nonetheless, two things are clear.
First, the number of severe cases — the product
of these two unknowns — becomes fearsome in country after country if the
infection is allowed to spread. In Italy, coffins of Covid-19 victims are accumulating in churches that have stopped holding
funerals. In Wuhan, at the peak of the epidemic there, critical cases were so
numerous that, if scaled up to the size of the U.S. population, they would have
filled every intensive care bed in this country.
That is what happens when a community waits until crisis hits to
try to slow transmission. Intensive care demand lags new infections by about
three weeks because it takes that long for a newly infected person to get
critically ill. So acting before the crisis hits — as was done in some Chinese cities outside Wuhan, and in some of
the small towns in Northern Italy — is essential to prevent a health system
overload.
Second,
if we don’t apply control measures, the number of cases will keep going up
exponentially beyond the already fearsome numbers we have seen. Scientists have
estimated that the basic reproductive number of this virus is around 2. That
means without control, case numbers will double, then quadruple, then be eight
times as big, and so on, doubling with each “generation” of cases.
To
stop an epidemic like that permanently, nearly half the population must be
immune. While the exact number of people infected in each population is
unknown, current estimates are that for every symptomatic case there is about
one asymptomatic or very mild case.
In
populations with good ascertainment of symptomatic cases, the number of
infections is perhaps double what is observed (in the U.S., where testing is
limited, true cases are a much higher multiple of reported cases). In
well-tested countries, we can be nearly certain that no population has reached
anywhere near half of its people infected. That means that when each country lets
up on control measures, transmission will increase and the number of cases will
grow again.
It is crucial to emphasize that a pandemic like this does not
dissipate on its own, as Ioannidis suggested as a possibility. Severe acute
respiratory syndrome (SARS) in 2003 was hammered into submission by intense
public health measures in many places, which were effective because
transmission was mainly from very sick people. Middle East respiratory syndrome
(MERS), which emerged in 2012, is a weakly transmissible infection that causes
outbreaks in hospitals, but is otherwise much less contagious than Covid-19.
There
are two options for Covid-19 at the moment: long-term social distancing or
overwhelmed health care systems. That is the depressing conclusion many epidemiologists
have been emphasizing for weeks, and which was detailed in an analysis released
this week by the Imperial College London.
Ioannidis
is right that the prospect of intense social distancing for months or years is
one that can hardly be imagined, let alone enacted. The alternative of letting
the infection spread uncontrolled is equally unimaginable. We certainly need
more data. Even more than that, we need a breakthrough to make effective
treatments, vaccines, or other preventive measures available at scale.
Waiting
and hoping for a miracle as health systems are overrun by Covid-19 is not an
option. For the short term there is no choice but to use the time we are buying
with social distancing to mobilize a massive political, economic, and societal
effort to find new ways to cope with this virus.
Marc Lipsitch, D.Phil., is professor of epidemiology at the
Harvard T.H. Chan School of Public Health and director of Harvard’s Center for
Communicable Disease Dynamics.