NY COVID contact tracing data: What it tells us, and what it doesn't

Jon Campbell
New York State Team

ALBANY – For the first time, New York has released statewide data that provides a glimpse into where residents are being exposed to the coronavirus.

Gov. Andrew Cuomo on Friday released a chart showing the various settings where New York residents are coming into contact with the virus, including a large share of cases traced back to small gatherings in households.

The data, which covers cases from September through November, is a compilation of cases handled by local contact tracers throughout the state.

But the data has its limitations. It's hindered in part by more than 170,000 cases over the same time period where a known exposure source couldn't be determined or an infected person didn't cooperate.

Here's what to know about what New York's recently released contact tracing tells us, and what it doesn't:

What kind of contact tracing data did NY release? 

Cuomo, during his COVID-19 briefing Friday, released a single chart that showed the percentage of confirmed coronavirus cases traced back to an exposure at 30 different industries, sites or situations. 

The chart did not include raw data. Instead, the governor's office said it was based on approximately 46,000 cases from September through November where those infected with COVID-19 were able to identify where they came into contact with the coronavirus through contact-tracing interviews.

The information was gathered contact tracers spread throughout the state, most of whom are employed by local governments.

The top six sources of exposure, according to the chart:

  1. Household/social gatherings (73.84%)
  2. Healthcare delivery (7.81%)
  3. Higher education student (2.02%)
  4. Education employees (1.5%)
  5. Restaurants and bars (1.43%)
  6. Travel/vacation (1.06%)

Among the locations toward the bottom of the list: Hair and personal care (.14%), gyms (0.06%) and child care (0.5%).

That's in large part why Cuomo decided to ease restrictions for gyms and salons, allowing them to reopen in state-designated orange zones on Monday.

More:NY COVID tracker: More than 10,000 new cases reported Sunday

The data comes with a huge caveat

The chart is based on roughly 46,000 cases. But New York had 219,755 confirmed cases from September through November, according to the Department of Health.

What about all the other cases? Therein lies the major caveat.

The 46,000 cases included in New York's chart are the ones where contact tracers were able to confirm a known source of exposure in an interview with the infected person.

That represents only about 21% of the total cases during that time period, and it's not necessarily a representative sample.

For the remaining 79% of cases — 173,000 or so — contact tracers either couldn't immediately determine a source of infection or the infected person declined to cooperate and provide their contacts, according to Cuomo's budget director Robert Mujica. 

In some cases, the contact tracing process is ongoing, he said.

"This information specifically is where we know the contact tracers have identified the source, they know what the source is, and it’s traced back to all of the sectors in that chart that the governor presented," Mujica said Friday.

More than 70% of cases from household spread? Not really

On Dec. 2, Cuomo's office unveiled a COVID-19 public service announcement that made a bold claim: "Over 70% of cases can be traced to your households and small gatherings."

The data released Friday shows that claim isn't quite true.

Of the 46,000 cases with known sources of exposure, 73.84% were connected to households or social gathering, according to the state.

But that stands to reason: Cases spread through households and small social gatherings — a wife who catches it from her husband, or a group of friends who all test positive after a dinner party, for example — are the easiest to contact trace.

It's relatively simple to trace an exposure to someone living in your household; it's far more difficult to trace it to, say, an interaction in a grocery store.

Since the pool is limited only to those with a known exposure source -- which, again, is only about one-fifth of the total cases -- the data is heavily skewed toward households and small gatherings.

When including the huge number of cases where there is no known source of exposure, the percentage of cases that can be traced to households and small gatherings is actually closer to 15%.

New York currently prohibits gatherings of 10 or more at private residences.

More:New York is among states limiting private gatherings to 10 people, but how will it be enforced?

More:What to know about New York's new COVID rules for gyms, salons, dining

What does the data actually tell us?

Stacey Cudzilo, owner of Park Avenue Salon & Day Spa  carries in products as the shop prepares to reopen for customers.

For one, few cases seem to definitively point back to gyms, fitness centers, barber shops and salons, all of which were previously subject to closure orders when within a state-designated "orange" zone, a cluster area that carries extra restrictions.

On Friday, Cuomo announced he would allow gyms and hair-care businesses in orange zones to reopen, with gyms limited to 25% capacity and salons required to test employees weekly.

Cuomo said the low numbers show the state restrictions at gyms and salons are working.

"Gyms and salons, as you also see, they are not the problem that they were," he said. "We have restrictions. The restrictions made a difference."

About 1.43% of cases with known exposure sources were traced back to restaurants and dining, according to the state data. While that remains a small percentage of the overall infections, it was the fifth-highest source of infection identified by the state.

Cuomo is banning indoor dining in New York City starting Monday, when he said he will also decide whether to further restrict capacity in the rest of the state.

More:NY revises COVID limits on restaurants, gyms and other businesses

More:COVID-19 vaccine: What we know (and don't know) about New York plan to end pandemic

Jon Campbell is a New York state government reporter for the USA TODAY Network. He can be reached at JCAMPBELL1@Gannett.com or on Twitter at @JonCampbellGAN.

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