Using Data and Evidence to Shape Cambridge's Public Health Response

With data surrounding COVID-19 being in the spotlight, The Cambridge Life staff spoke with Anna Kaplan, MPH, to better understand the role that data plays in Cambridge’s public health response. Anna is an epidemiologist with the Cambridge Public Health Department.

Thank you for talking with us. Can you start by telling us what epidemiology is?

That’s a great question. Epidemiology is the study of the spread of disease. We try to figure out how disease outbreaks or illnesses are connected to people’s daily experiences and behaviors. There’s a classic story taught in almost every epidemiology class I’ve ever taken about early cholera epidemics. An early epidemiologist, John Snow, noticed in the 1830s that people in one London neighborhood were getting sick. After mapping all the houses where people were sick in the neighborhood, he realized that all the households had a connection to one particular water pump. After the water pump was closed, people stopped getting cholera in that neighborhood. Zooming back to the present moment, the building blocks of epidemiology rely on the same basic principles of who is getting sick and why.

As an epidemiologist, how do you fit into the Cambridge Public Health Department?

Currently, I manage and analyze all data connected to COVID-19. Some days I am investigating clusters, other days I am creating and interpreting maps and trend lines. All of the data and visualizations you see in Cambridge’s COVID-19 webpage, come from data that my team works on.

I am also involved in some of the nitty gritty work, like contact tracing, where we work to understand why clusters happen and how to prevent further spread. For example, I did a lot of work with Cambridge’s long-term care facilities in the spring. We used the data we were seeing to understand how COVID-19 is spread and provide evidence-based guidance to prevent more people from getting sick. If we understand more about why and how this disease spreads, we can better implement interventions to prevent it. If you have received a call from one of the Public Health Nurses in Cambridge, you have helped contribute to this work!

How does your work help the City use data in its decision making?

Most people have now heard about the idea of the “curve” and how we need to flatten or bend it. An epidemiological curve (“epi curve”) is one of the foundational tools in our field. Basically, you plot the number of new cases each day over time. If the slope is up (positive), that means spread of the disease is increasing, and if the slope is downward (negative), that means the spread of the disease is decreasing. This information then guides decision making in the City.

When we see the slope going up, we know we need to change strategies. And when we see the slope going back down, we know transmission is decreasing. We overlay Cambridge’s epi curve with the dates specific interventions were introduced to help us understand potential impact. This includes the different reopening phases, major holidays, or when our face coverings order went into place.

Because COVID-19’s incubation period is about 14 days, we can often see the impact within about two weeks after an important date or policy change. Depending on the behavior of our residents (or visitors) in the City, we may see more or fewer cases. As an example, after Memorial Day and July 4th, we saw a small bump in cases, likely from people socializing in person more. But when the mask order went into effect, we saw cases go down.

Can you give us an example of how data, like what is on the COVID-19 Data Center, have been used in the City’s efforts to fight the virus?

Much of the data that we are using internally for decision making is also being shared with the public via Cambridge’s COVID-19 Data Center at For example, the neighborhood-based data helped us decide where to locate our mobile testing sites. The City’s community mobile testing program started in The Port because people who live there were being disproportionately impacted by COVID-19. High- quality data and mapping helped support advocacy at the neighborhood level to provide testing locations where they were needed. Providing testing in high transmission areas helps us stop the spread, by identifying low-symptom or asymptomatic cases and supporting them to isolate and their contacts to quarantine.

Where do you get your data from?

The way we get data as a city health department is through the state database called the Massachusetts Virtual Epidemiologic Network (MAVEN). All labs in Massachusetts report positive COVID-19 results to the state, and anyone with a Cambridge address gets filtered down to us. Our department was one of the earliest adopters of MAVEN in the state. Sometimes you will see the case count go down by one or two cases from the reported number from the day prior, because we find out during the contact tracing process that someone actually lives in another community. These case records contain lots of information, including all linked cases and contacts, demographic data, and clinical data.

Why doesn’t the City release more data or information about who is infected?

There’s a challenging balance between privacy and data transparency. We are very deliberate in the data that we release. We want our decision making factors to be transparent, so that the public understands why the City introduces or rolls back public health regulations. And while data transparency is important, the need to keep residents’ personal health information private is a critical responsibility of the department. Also, we have gained more information over time, which allows us to improve the information we share with the public!

Why should the public be interested in the data being released?

Something I have learned a lot about over the course of the last few months is that data on its own is not enough to guide us through COVID-19. We need clear data visualizations paired with qualitative data on people’s experiences, so people grasp what is going on in the community to understand and advocate for additional policy changes. Data can help ground our personal decisions in facts and help us not be inadvertently persuaded by misinformation or the latest rumor about the virus. The City, by having a transparent data communication strategy, can help our residents understand what is happening in our community, help people assess their own risk, and help residents make choices that will positively impact their lives and keep their families and community safe.

What has the experience of doing your work during a pandemic been like for you?

During all of this, we’ve felt pretty reactive and like we’re moving at high speed, but public health at its core is all about prevention. One of the things that’s key to public health is that we consider how many parts of people’s lives impact their health, and intersect with infectious disease like the coronavirus. For example, climate change and racism are huge public health issues. So I’m hopeful that people with power are learning from this pandemic, and will prioritize public health in the future. On a personal note, my parents, friends, and family now have a much stronger understanding of what I do. They’re like, “Oh, epidemiology, like those people I’ve seen on the news...I get it now!”

Page was posted on 9/3/2020 2:30 PM
Page was last modified on 9/3/2020 2:44 PM
Contact Us

How can we help?

Please provide as much detail below as possible so City staff can respond to your inquiry:

As a governmental entity, the Massachusetts Public Records Law applies to records made or received by the City. Any information received through use of this site is subject to the same provisions as information provided on paper.

Read our complete privacy statement

Service Requests

Enter a service request via Commonwealth Connect for things like missed trash pickups, potholes, etc., click here