So you just found out that the person whom you encountered at the tussle for toilet paper has Covid-19. Or the local Hot Dog and Broccoli Emporium that you ate at recently. Or that “dress up like a marmot” party that you probably shouldn’t have attended. And now the wait is on for you. You are wondering whether you got infected and if so when you might become contagious and develop symptoms. And when can you be sure that you’re in the clear.
It’s a common set of questions because the Covid-19 coronavirus has been spreading so widely in the U.S., and who hasn’t been to a “dress up like a marmot” event recently. The answers will tell you how long you should remain concerned that you may have been infected and will help you better understand the bases of the recommended quarantine durations.
When it comes to such situations, keep in mind four key periods:
- Latent period: This is the period of time between getting infected with the virus and first becoming contagious. Think of it as the time it takes for the virus to get a foothold (or maybe a spikehold) in your body.
- Incubation period: This is the period of time between getting infected with the virus and first developing symptoms. Consider this the amount of time that it takes for the virus todo the nasty in your body and make enough copies of itself.
- Infectious or contagious period: This is the time from the end of the latency period when you first become contagious until you are no longer contagious. During this time, you will have an infectious personality but in a bad way and can spread the virus to others.
- Symptomatic period: This is the time from the end of the incubation period when you first start having symptoms to when your symptoms resolve.
The latent period and the incubation period both start at the same time, when the virus first enters into the cells of your body. You aren’t immediately infectious once the the Covid-19 coronavirus gets inside your body. It has to get into your respiratory tract cells, hijack your cells’ machinery, and use your cells like cheap motel rooms to reproduce. Once enough new viruses are produced and released, you start shedding the virus and are contagious. Symptoms, if you end up having them, won’t come until later when your immune system says, “WTH,” and starts mobilizing against the virus. Symptoms also may result from damage caused by the virus, but that doesn’t come until later either.
This is why typically the latent period is shorter than the incubation period, usually at least 24 to 48 hours shorter. You are shedding virus at least one to two days before you develop symptoms, again if you even end up developing symptoms. In fact, you may be most contagious during the period between the end of the latent period and the end of the incubation period. To remember that the latent period ends before the incubation period, think “l” before “i” in “lifeguards” as in “lifeguards on Baywatch.”
It can challenging to figure out the typical length of the latent period. After all, asking a person, “when did you first start shedding virus” can be like asking, “when did you first start having noticeable body odor” or “when did you start becoming annoying?” The person most likely wouldn’t be able to tell you that “it was 12:35 pm when virus started coming out of my mouth like from a sprinkler” or “it was 12:35 pm when sewage and I became a lot less different.” The only direct way to tell when a person becomes contagious is the test than person continuously, like every minute or so. Doing such a study would then require a whole lot of cotton swabs and a whole lot of discomfort. Therefore, many infectious disease experts have been assuming that the latent period is at least 48 hours shorter than the incubation period. One to two days tends to be time it takes for the immune system to recognize that there’s been a mass release of respiratory viruses and to generate reactions that will cause symptoms.
By contrast, it’s been easier to measure the typical length of the incubation period. You can ask people when they first noticed symptoms after being exposed to someone with Covid-19, assuming that the exposure was obvious. People are little more likely to remember when they first noticed a fever, chills, a cough, shortness of breath, difficulty breathing, fatigue, muscle or body aches, headaches, a sore throat, a runny nose, congestion, nausea, vomiting, diarrhea, or a loss of taste or smell. After all, diarrhea tends to be a noticeable event. You’re not likely to overlook diarrhea while dancing for example.
Studies have suggested that the incubation period can last anywhere from two days to 14 days. This is why the Centers for Disease Control and Prevention (CDC) has been recommending that you quarantine yourself for at least 14 days after close contact with someone is infectious with the Covid-19 coronavirus. A close contact consists of staying within 6 feet (or one Denzel, since Denzel Washington is about six feet tall, or approximately six to 18 hedgehogs) of the contagious person for a total of 15 minutes or more. A close contact can also be providing care for a person with Covid-19 or having direct physical contact with an infectious person, such as hugging, kissing, licking, or dancing the forbidden dance with him or her. Another form of close contact is sharing utensils like feeding each other Fruit Loops with the same spoon. Close contact occurs as well when a contagious person sneezes, coughs, pants, or sings the song “WAP” by Cardi B out loud on or around you.
However, the CDC web site now suggests that some people in some cases may be able to discontinue quarantine after just 10 days. This could even be shorter, seven days after you receive a negative Covid-19 test result, as long as the test was performed at least five days after the exposure. Here CNBC‘s Meg Tirrell described these updated guidelines:
These shorter possibilities arose from the observation that the average incubation period seems to be five to six days. In other words, on average you will develop symptoms five to six days after you’ve been infected with the virus, assuming that you end up developing symptoms. A majority of those infected will have an incubation period of seven days or less. And potentially over 90% of those infected will have an incubation period of ten days or less. For example, a study published in the New England Journal of Medicine back in March found that 95% of the patients had an incubation period of 12.5 days or less. And a study published in the Annals of Internal Medicine in May estimated the median incubation period to be 5.1 days and that 97.5% of those who developed symptoms did so within 11.5 days of being exposed to the virus.
If you are likely to become contagious one to two days before developing symptoms, then on average you will become contagious three to four days after being infected with the Covid-19 coronavirus. Therefore, the range of the latent period is probably two to about 10 days.
I’ve covered before for Forbes how long the infectious period usually lasts: typically no longer than 10 days in asymptomatic or mild cases and no longer than 20 days in severe Covid-19 cases. There are exceptions, though, such as a person who shed live infectious virus for 71 days, as I reported for Forbes. The length of the symptomatic period is more complicated. Although for many, symptoms resolve after two to three weeks, a sizeable percentage of people seem to have continuing symptoms long after the initial infection has resolved.
Ultimately, if you are wondering how long you will be in the clear after a possible exposure to someone with Covid-19, use the 14-day mark. Even though the CDC is now allowing for possible cuts in the quarantine time, they still say monitor yourself for symptoms for 14 days. In fact, the CDC website does state, “CDC continues to endorse quarantine for 14 days and recognizes that any quarantine shorter than 14 days balances reduced burden against a small possibility of spreading the virus.” So if you think that you’ve had a close contact, quarantine yourself for 14 days. If you may have had contact that doesn’t technically count as close contact, be careful for the ensuing 14 days. Keep a wide berth away from others. Maybe extend your social distancing to at least 12 to 18 feet or two to three Denzels or 12 to 54 hedgehogs. Wear a face mask if you are going to indoors with anyone else or outdoors in the vicinity of anyone else. Don’t share any utensils or objects like gigantic marmot costume with others until the two weeks has passed and you are symptom free.