Testing, Tracing, Containing: COVID Response Strategies are Anything but New

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Discovering Public Health

For many people, COVID may be the first time you’ve thought about public health beyond things like the existence of vaccines. You may never have known that some diseases have to be reported straightaway to health authorities and that someone calls you if you’ve tested positive. You may never have heard of an epidemiologist or thought that we do something with skin.

Since COVID, though, you’re likely hearing terms like “contact tracing,” “quarantine,” and “isolation” all over the place. You may have heard about PCR testing and serological surveys using antibody testing. It’s possible you’ve even become a bit of an armchair epidemiologist. It might be the first time you’ve heard these words, but they’re far from new to public health. Below I talk a little about some terms you may have heard related to public health and some of their history.

Tools of Disease Control

Case and Contact Tracing — When someone is diagnosed with a reportable condition (one which needs to be reported to health authorities, like measles or chlamydia), an investigation is launched into how the person became infected and to identify anyone they may have made sick while they were infectious. This is a standardised process and epidemiologists use all kinds of fancy tricks to trace back where cases (the sick person) might have been and to find out who was with them (their contacts).

If you live in the United States, the local health department (usually associated with a county) where you live will likely conduct the investigation, even if you were diagnosed in another county.Case investigators (also called contact investigators) may ask you to review places you’ve checked in on social media or your photos from the last few weeks. If you have a foodborne illness, they may ask for your shopper’s reward card to determine which exact package of blueberries you purchased 3 weeks ago so that the farms and packing plants can be identified. The process is painless, but it can take an hour or two to get through all the questions depending on their outbreak and how much information the health department already has. It’s a long time to sit on the phone, but investigators are trained to go as quickly as possible through the questions so you can get back to your day.

Because someone asked me recently and I want to be very clear: investigators do not come to your house to haul you away if you test positive for COVID. Public health investigators may offer places for you to quarantine or isolate away from your family if you can’t do so in your own home or if you’re living homeless, but these places are not requirements. In my county, the health department has purchased hotels where people are offered a room if they, for example, test positive and are not able to keep themselves separate from a household member who is more likely to have a severe infection (like a grandparent or pregnant partner.

Quarantine — You’ve likely been hearing this word a lot lately. Unfortunately, you’ve likely also been hearing it used incorrectly. While we’ve all (hopefully) been staying home, we have not all been in quarantine. Quarantine is a term which refers very specifically to staying home for a designated period (14 days for COVID) after you were exposed to a disease. To meet the criteria for quarantine, you also need to be symptom-free. If you do have symptoms, then you’re isolating.

For example, if your coworker tests positive for COVID and you’ve been working next to him for more than 10 minutes in the last 14 days, you will likely be asked to quarantine until 14 days after your last exposure to your coworker. During this time, you’ll need to monitor yourself for symptoms like a cough or fever and your local health department will likely call you periodically to check in if you don’t let them know you’re still symptom-free. If you haven’t been exposed, you’re not in quarantine.

Isolation — Isolation seems to get batted around less, but is also an important component of controlling communicable diseases. You’re isolating when you’ve been exposed to a disease and are symptomatic (i.e., you have the symptoms of the disease). While health officers don’t usually like to issue orders forcing people to isolate, they do usually have that legal authority and will do so in some circumstances. For example, a health officer may order a healthcare worker with tuberculosis to stay in their home to prevent them infecting their community while they’re being treated for the disease.

Antibody testing — Antibody testing is popping up in conversations a lot recently and there are some misconceptions about what it is (and isn’t). The most basic explanation of antibody testing is that it looks for evidence of the antibodies your immune system creates in response to an infection. This is different than the testing that health departments use to create their case counts (the count of people infected), which look for the presence of the virus in your body. If you’d like to learn a bit more about antibodies, I talked about them here when I wrote about how vaccines work.

Historical Application of Disease Control Tools

Humans didn’t always control outbreaks the way we do now because we didn’t always understand that communicable diseases like plague, measles, and syphilis are spread by pathogens like bacteria and viruses. For a long time, humans thought that diseases were spread by miasma or bad air. After pioneering epidemiologists like John Snow and microbiologists like Louis Pasteur proved that at least some diseases were caused by microscopic lifeforms which could be passed from person-to-person. When Dr. Snow investigated the 1854 outbreak of cholera in Soho, London, he wasn’t just trying to stop an outbreak—he was trying to prove that cholera was spread through the water rather than through “bad air.” He was trying to save lives and prove that his theory of disease transmission was correct.

Even without understanding how diseases were transmitted, though, many of the tools we use now to control the spread of disease stretch back centuries (or even farther). Some diseases (like plague) required reporting and what we now call “non-pharmaceutical interventions” (like closing pubs and schools) were applied when magistrates thought them necessary. Isaac Newton was a student at Trinity College during the “Great Plague” in 1665 and was sent home when the school closed to prevent the spread of plague. During that time, he did some of his best work exploring what would become calculus, looking through prisms, and describing gravity.

Daniel Defoe, author of Robinson Crusoe and Moll Flanders, wrote another book about that same Great Plague of 1665, Journal of the Plague Year, which may be based on his uncle’s diary from the time. In Plague Year, Defoe discusses what it was like to live through the period, as well as outlining some of the legal orders issued to stop the spread of plague in 1665 London, including:

  • “Notice to by given of the Sickness” to the local “examiner of health” should someone fall ill,

  • “Sequestration of the Sick” when someone falls ill for a month,

  • “Shutting up of the House” which required that anyone who enters a house with plague should be “shut up for certain days by the examiner’s direction,”

  • “Hackney coaches” (taxis) shall be thoroughly aired and left empty for a period of 5 or 6 days after transporting someone with plague,

  • “None to be removed our of infected Houses, but, &v.” that “none be removed out of the house where he falleth sick of the infection into any other house in the city,” and

  • “Burial of the Dead” shall not have “common prayer, sermon, or lecture” which forbid children attending any funeral

You might notice there that not only the reporting of the disease is required, but also that people exposed should be kept sequestered (apart from others) and that a house with the sickness should be “shut up” (isolation and quarantine). Even the equivalent of our modern taxis were required to decontaminate, which is reminiscent of the way we’re now sanitising our busses at the end of every day. The magistrates also issued orders that all plays, “feasting,” and pubs must close, which is a list very similar to the social distancing orders we’ve been living under in lockdown.

Even the term “quarantine” is old. It dates back to the waves of plague (the “Black Death”) in the 14th century and comes from the Italian word quarantena which referred to a 40 (quaranta) day period of keeping ships from docking and unloading to prevent the spread of plague in Venice. Venice was heavily involved in trading and understood all too well that plague could be carried into their community. They didn’t understand that it was rats and fleas infected with yersinia pestis bringing it, but they knew that plague could be brought in by outsiders.

During the 19th century, yellow fever (a flavivirus related to dengue, chikungunya, and Zika) terrified sailors and port cities. Viruses are too small to see using the microscopes available at the time and the connection between mosquitoes and the infection was still unknown. Before a vaccine was finally developed in 1927, port cities would quarantine ships coming into their harbours to protect themselves from the sickness they knew it might bring to them. If you’re interested in learning more about yellow fever, vector control, and the development of its vaccine, I highly recommend Mariola Espinosa’s Epidemic Invasions: Yellow Fever and the Limits of Cuban Independence, 1878-1930.

Additional Resources to Consider

I mentioned several books above which might be of interest for you if you’d like to learn more about the history of public health.