On the morning of March 28, Domingo Vega of
Queens, New York, went to the hospital with
symptoms of pneumonia and tested positive
for Covid-19.
This is Domingo. But not just him. This light
represents 500 people who have been infected
with the novel coronavirus in New York City.
By May 16th, there were nearly 190,000 known
cases of Covid-19 there.
Health officials report these numbers every
day, in cities and countries around the world,
but they know that they’re incomplete. Because
Covid testing has been like a narrow flashlight
in a dark room. Anything we’re not pointing
the light at, we can’t see. 
But now researchers are collecting data that
can capture the pandemic more fully, to try
to get a better handle on just how much we’ve lost.
Domingo Vega died on April 16th at the age
of 45. Originally from Mexico, he came to
the US when he was 16, and worked in restaurant
kitchens since then, eventually launching
his own business with two locations in Brooklyn.
He and his wife had three children. 
Domingo was one of 20,720 New Yorkers whose
lives were cut short by the coronavirus as
of May 16th, according to the city’s count.
Each blue light here represents 500 known
deaths from Covid-19 and 500 families who
don’t need data to tell them how dangerous
this disease can be.
But when it comes to the statistics, that
question -- how deadly is Covid-19 -- has
been difficult to answer.
The relationship between the known deaths
and the known cases is called the “case
fatality rate.”
At this point in New York City, 1 out
of 9 people known to have Covid-19 have died.
That’s 11 percent.
But that rate varies drastically across cities
and countries. It was over 12% in Sweden in
mid May but less than a percent in Iceland.
It also changes over time. For the US, it
dropped down to 1% near the end of March before
climbing back up as people who tested positive
several weeks prior ended up dying.
When the case fatality rate varies this much,
it’s saying a lot more about these countries
than about the disease itself. 
For example, deaths may be higher in places where
the health system is overwhelmed 
or where the population is older. We know
that Covid-19 is more deadly in seniors, and
especially those over 75.
But also, on the other side of the fraction,
the rate reflects how much testing is happening.
If a country is aware of more non-fatal cases,
their case fatality rate is lower.
So this statistic isn’t all that useful
because we know most countries are missing
cases. We’re also missing deaths.
According to an estimate by the New York Times,
there have been thousands of deaths that weren’t
included in the official count for New York
City. 
We don’t know for sure if it was coronavirus
that killed them. But here’s what we do
know.
If you look at 2017, 2018, and 2019, and chart
the average number of deaths per week, the
line looks like this. It includes deaths from
all from all causes.
For 2020 so far, that line of weekly deaths
looks like this. The area above the typical
level is called “excess deaths” by researchers.
And it gives us a fuller picture of the cost
of this pandemic.
We’re seeing excess deaths in many places
that have suffered big outbreaks. 
In each case the excess deaths are higher
than the official count of Covid deaths. 
It includes people who may have died from
other causes but who were unable or unwilling
to access medical care because of the pandemic.
But it also includes some people with coronavirus
who may have died at home or care facilities,
or were never diagnosed.
As this data comes in, it shows that in some
places, the pandemic is even more deadly than
we thought.
But the virus itself may be less deadly. Because
we’re also learning that a lot more people
have been infected than the official tallies
show.
Health officials in New York have taken small
blood samples of people at grocery stores
to check for Covid antibodies. This is called
a “seroprevalence survey” and it helps
capture the substantial number of people who
didn’t know they ever had coronavirus.
So far these tests show that around 20% of
people in New York City tested positive for
antibodies that indicate a previous Covid
infection.
If those shoppers are representative of the
city’s population, that would mean there
were more than one and a half million Covid-19
cases in the city by early May.
Without changing how many people have died,
the antibody survey lowers the fatality rate
by identifying more non-fatal cases.
Remember the case fatality rate was 11% one
in 9, but the fatality rate for all those
infected may fall somewhere between 1 in 60
and 1 in 90 for New York City.
So while the death count is higher than we
thought, the death rate may be lower. But a low
fatality rate is not all good news.
It paints a picture of a tricky virus that
moves undetected through many of us and causes
immense suffering and death in others.
We can look for comparisons to try to wrap
our heads around the death toll - more people
lost in three months in the US than a year’s
worth of car crashes or drug overdoses. Still
fewer than annual deaths from cancer or heart
disease. 
But the comparisons are limited. Because unlike
car accidents or cancer, Covid-19 is contagious.
Human beings are the vector for this disease
and their actions are hard to predict.
So even with better data about how many are
infected and dying, we won’t know the full
death toll of this pandemic
until we find out how it ends.
