UPDATE: This article has been updated with new information on September 12, 2020, 6:00 a.m.

A recent survey of 1,269 people across 113 hospitals in New York discovered a confusing statistic: 66% of patients who were newly diagnosed with coronavirus disease 2019 (COVID-19) were staying home but still got sick with COVID-19. 

Researchers were perplexed by this number because it’s not what they expected. Instead, researchers had assumed most new cases would be from healthcare workers and other essential workers, since these are the people leaving their homes, using public transportation, and coming into contact with others on a regular basis. They didn’t expect the majority of cases to be in people who said they hadn’t left the house.

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So, what’s going on here? Presumably, the whole point of sheltering in place and social distancing has been to help prevent the spread of COVID-19. But if people who are staying home are still getting sick (and in even higher numbers), has it been working? Why is this happening?

Before diving into the reasons why this may be the case, there’s one possibility to consider: The results of the survey simply aren’t accurate. A survey isn’t the same as a randomized controlled trial (or like most scientific studies you’re probably used to hearing about). Surveys can be useful for getting a snapshot of a certain topic, but they are also much more susceptible to bias than other types of studies and they don’t provide solid evidence.

For example, some of the patients in the survey may not have actually remembered if they left the house or not but answered “no” anyway. Or, some of the patients might have known they left the house but were too embarrassed to admit they had. The point is, doing a survey isn’t the best way to collect accurate scientific information.

However, if we assume the results are accurate, there are a few reasons why people who have been staying home may be getting sick:

1.     Not actually staying 100% isolated: Staying home is one thing, but being 100% isolated from the outside world is another. It’s possible some of these patients stayed home most of the time, but left once or twice for essential items, like groceries. Or, maybe the patients stayed home all of the time but somebody else in the household didn’t and was going back and forth, potentially carrying the virus. Getting a food delivery (or any other delivery) could also be one way to get exposed to the virus. And, especially in New York, there are many people living in close proximity to one another. Using a communal elevator, or laundry room, or sharing circulating air could be another way to get exposed to the virus while still technically staying at home.

2.     The incubation period of COVID-19: After getting infected with COVID-19, it takes most people 11.5 days to develop symptoms. For some, it may take even longer — possibly over a month. Therefore, there’s a chance that some of the patients were actually infected before they started staying home — it just took a while for their symptoms to show up. 

3.     Factors we still don’t understand: There’s also a lot we still don’t understand about COVID-19. Over the summer, new symptoms like “COVID toe” (toe lesions caused by COVID-19) and an inflammatory condition that affects children were reported in the news. Every day, we learn more about the virus and we realize how much more there still is to learn. It’s very possible that the COVID-19 virus is spreading amongst people staying at home in a way we don’t yet understand.

Thinking beyond this survey and COVID-19: If you’ve been staying at home but feel like you’re getting sick too, there are a couple of explanations why. First, not all disease-causing organisms spread the same way. Some travel farther through the air than the COVID-19 virus, and some can linger in the air for longer than the COVID-19 virus. Some illnesses come from food, and some come from plants or animals. So even if you’ve stayed home and entirely avoided contact with others, it’s still possible to get sick.

This also happens to be the time of year that many people experience allergies. If you feel congested, have a runny nose, and itchy/red eyes, it’s possible you have seasonal allergies brought on by the change in weather. And allergies don’t only occur outdoors. If you’re spending more time inside with a pet or where there might be mold or dust mites, you could experience symptoms that make it feel like you’re getting sick (if you have a fever, though, it probably isn’t allergies).

All-in-all, the results of the New York survey may have been surprising — but they shouldn’t be enough to convince you that all of this has been in vain. Death rates and rates of new infection are down in many areas, thanks in large part to the stay-at-home and social distancing efforts of everybody. So, even though it may still be possible to get sick at home — whether through accidental exposures or because the virus spreads in a way we have yet to discover — it is still much less likely than if you leave the home. Remember to continue following the guidelines where you live and keep an eye out for any further news about the virus.


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