Argh, you’re feeling sick again. You don’t want to take off work or go to the doctor if you don’t have to, but you also don’t want to be that person who infects the whole office. You might have toughed it out before the pandemic, but the etiquette is different now. So how can you be sure about what you have, or if — and for how long — you need to stay home?
Here’s what infectious disease experts want you to know about some of the most common adult and pediatric viruses (and one bacterial infection): their symptoms, how they spread, how to treat them and when you (or your child) can reenter society.
— Cold
Mild symptoms, including runny nose and congestion. Most contagious on days 2 and 3.
“Cold” is a catchall term for a mild respiratory infection. It’s most commonly caused by a rhinovirus, but adenoviruses, coronaviruses, parainfluenza viruses and metapneumovirus can also induce cold-like symptoms.
“We recognize it as being sort of the fallback diagnosis,” said Dr. Stuart Ray, a professor in the division of infectious diseases at Johns Hopkins Medicine. In some people, a COVID-19, flu or RSV infection might result in mild symptoms and be mistaken for a cold.
Symptoms
Cold symptoms are familiar to most people: sore throat, runny nose, congestion and cough, sometimes combined with headache or fatigue.
Fever, muscle aches and lower respiratory symptoms — such as shortness of breath, wheezing or chest pain — are signs that you might have a more serious infection, like the flu or RSV.
“Neck and above is usually common cold, and down below is often something else,” Ray said. Symptoms typically last about five to seven days, peaking in severity around Days 2 and 3 and tapering off after that.
How it’s spread
Rhinoviruses are spread primarily through droplets, meaning you breathe in what someone else coughs, sneezes or breathes out. They can also survive on surfaces for up to 24 hours, and you can become infected by touching your face after picking up virus particles from something like a door handle or TV remote control.
It typically takes a day or two after you’ve been exposed to a rhinovirus until you develop symptoms.
How it’s treated
There are no antiviral treatments for the common cold, but some over-the-counter medications and home remedies may help relieve symptoms. (Be sure to check medication labels: One common decongestant ingredient, phenylephrine, was recently deemed ineffective by an advisory committee to the Food and Drug Administration.)
How long you are contagious
You are most infectious when you feel the worst, typically during the second and third days of symptoms. As you begin to feel better, the amount of virus in your body drops quickly, and it’s generally safe to assume that you’re no longer very contagious after day 3 or 4, said Dr. Patricia Whitley-Williams, a professor of pediatrics at the Rutgers Robert Wood Johnson Medical School.
Don’t worry if you still have a cough at that point; Ray said that this is because the airways can remain inflamed from the body’s immune response, not because the virus is still present. However, you should continue to practise good hygiene, like coughing into your elbow and frequently washing your hands. If you have a lot of mucus or other symptoms, you should behave as if you are still contagious.
There’s debate over whether you need to stay home when you have a cold. Though colds typically are not risky, they are unpleasant and inconvenient, which can be reason enough to avoid spreading them to others. More important, if your cold is actually COVID or RSV, it could be dangerous for someone else.
— Norovirus
Diarrhea and vomiting. Symptoms last 24 to 48 hours, but you can be contagious for weeks.
Norovirus is the most common cause of short-lived gastrointestinal illnesses. If you have ever had a stomach bug, chances are it was norovirus, said Dr. Ferric Fang, a professor of laboratory medicine and microbiology at the University of Washington School of Medicine.
Symptoms
Norovirus symptoms come on suddenly and typically last one to two (miserable) days. They include diarrhea and vomiting, as well as nausea and stomach pain.
How it’s spread
Norovirus is incredibly contagious — just a few viral particles can infect someone. Once a person comes into contact with the virus, it usually takes a day or two until symptoms hit.
The virus is most commonly spread through particles left on surfaces and objects by an infected person who did not wash their hands properly after using the bathroom (the so-called fecal-oral route).
Dr. William Schaffner, a professor of preventive medicine at the Vanderbilt University School of Medicine, said he remembered a bridge club in which all of the members caught norovirus because their playing cards were contaminated. “You pick up the cards, you get the virus on your finger,” he said, “and then if you touch your nose or your mouth, bingo.”
Norovirus particles can spread through food, too. It’s thought to be one of the primary causes of food poisoning — you get sick not from a food source, but from a sick food handler who contaminates the food.
It can also be transmitted via aerosols from vomit or diarrhea, so it’s possible to catch it if you’re in the same room as a person who is throwing up.
Because norovirus spreads so easily, hand hygiene and surface cleaning are essential when someone around you is sick. And hand sanitizer and gentle cleaners won’t cut it — you need to use soap and water for your hands and a bleach-based cleaner for contaminated surfaces.
“It’s extremely infectious, so if someone in your household has it,” the virus is very difficult to avoid, Fang said. He recommends having the person who is ill use a dedicated bathroom, if possible.
How to treat it
There is no real treatment for norovirus. In fact, doctors typically advise against coming in to see them when you have a 24 to 48-hour stomach bug because there is not much they can do for you, and you might spread the virus to other patients, Fang said.
You just need to ride it out and try to prevent dehydration — drinks that contain electrolytes, such as Gatorade or Pedialyte, are often recommended.
How long you are contagious
People can remain contagious with norovirus for weeks after their symptoms resolve because they continue to shed viral particles in their stool, though the levels are not as high as when they first fell ill.
Of course, it’s not realistic to stay home from work or school for that long, so once you are no longer vomiting or experiencing diarrhea, it is okay to return to the real world. However, you should continue to be extra vigilant about washing your hands after you use the bathroom.
— RSV
Severe coughing, wheezing, shortness of breath. Most contagious on days 1 to 5. Respiratory syncytial virus was once dismissed as just another mild cold virus, but it can be serious for infants and older adults. The severe consequences of RSV were on display last winter when it contributed to the “tripledemic,” alongside COVID and the flu.
“Infectious disease experts have appreciated how bad RSV is for a long time,” Ray said. But, he added, before last year, it had largely “flown below the radar” for the rest of us.
Symptoms
With mild cases, it can be hard to tell if you have RSV, as opposed to a cold, the flu or COVID; a runny or stuffy nose, cough, headache and fever can occur with all four diseases. However, experts say that RSV has a greater likelihood of affecting the lungs and lower respiratory tract, causing severe coughing, wheezing and shortness of breath.
“It tends to cause a lot of reactivity of your airways, so you cough and you wheeze a lot,” said Dr. Helen Chu, a professor in the division of allergy and infectious diseases at the University of Washington School of Medicine. Most symptoms typically last about a week, though a cough can linger long after other symptoms clear up.
How it’s spread
RSV is most commonly spread through droplets expelled in an infected person’s sneeze or cough that then get into someone else’s nose or mouth. It is possible for RSV to remain suspended in the air as tiny aerosol particles, but it is much less contagious in that form, said Dr. Edward E Walsh, a professor of medicine at the University of Rochester and the head of infectious diseases at Rochester General Hospital.
Regardless of the mode of transmission, infection is most likely to occur when you are within a few feet of the person, Walsh said. Backing this up, one small study conducted in the early 1980s that deliberately exposed people to infants with RSV found that the volunteers who picked up and held the sick babies were much more likely to get infected than the ones who were in the room but did not interact with them.
The virus can survive on surfaces for several hours, so there is also a risk of infecting yourself by touching contaminated objects and then touching your mouth, nose or eyes. In the study mentioned above, a smaller proportion of people got infected this way. It typically takes about five days after contact with the virus until symptoms develop.
How it’s treated
There are no antiviral treatments for RSV, but the over-the-counter medications and home remedies you use to relieve general respiratory symptoms may help.
As of this year, there are two vaccines for adults age 60 and older that protect against severe RSV. One of the vaccines is also approved for pregnant women in their third trimester so that they can pass on antibodies through the placenta to their newborns. Another new preventive therapy uses monoclonal antibodies to protect infants from severe RSV.
How long you are contagious
As with other respiratory viruses, you are most infectious during the first few days when you are most symptomatic; virus levels drop around day 5. After that, experts say it is safe to assume that you are no longer very contagious and you can go back to work or school — as long as you do not have a fever and are not producing a lot of mucus. If you will be around older adults or young children, it is best not to get too close to them for a few more days, just in case.
Keep in mind that you may still be coughing beyond day 5 because your airways can remain inflamed after the virus is gone. “Those are post-infectious coughs,” Walsh said. “They are no longer shedding infectious virus.” If you want to be extra careful, you can always wear a mask.
Words of warning
RSV can be deadly for the very young and very old. It is the leading cause of hospitalization for infants in the United States and results in 6,000 to 10,000 deaths per year for adults 65 and older. Seek medical attention if you or your child are having trouble breathing.
— Hand, Foot and Mouth Disease
Rash, mouth sores, fever. Most contagious while symptoms are present (a few days to a week). Hand, foot and mouth disease is caused by viruses in the enterovirus family, such as coxsackievirus. It is most common in children under age 5, but adults can contract it, too.
Symptoms
As the name suggests, the disease characteristically involves a rash on the hands and feet and sores in the mouth; children often develop a fever, too. Symptoms are usually worst in the first two to three days and last for about a week.
The rash looks like small red bumps, sometimes containing fluid — like little pimples. You do not want to pop these, since the virus is in the fluid and can potentially infect others.
The mouth sores — often the most painful part of the illness — are typically on the gums or the tongue and may stop children from eating or drinking. “That may be the first tip that they have sores in their mouth,” said Dr. Patricia Whitley-Williams, a professor of pediatrics at the Rutgers Robert Wood Johnson Medical School. If you take a look, sometimes you can actually see these ulcers, or little blisters or sores, she said.
How it’s spread
Enteroviruses that cause hand, foot and mouth disease are highly contagious and are spread primarily through saliva and stool. Hand washing is the best way to prevent the virus from spreading, but if one child falls ill, an outbreak in a day care center or school is hard to avoid.
“You see them most often in young children and toddlers because they share, unfortunately, saliva and stool in child care settings,” said Dr. Lori Handy, an infectious disease physician at Children’s Hospital of Philadelphia.
It takes three to six days after exposure to the virus for someone to develop symptoms.
How to treat it
There is no treatment for hand, foot and mouth disease, just symptom relief. That means taking fever reducers and pain killers, such as acetaminophen or ibuprofen. Be sure your child is still eating and drinking so they do not become dehydrated. Handy recommends cold, soft foods like ice pops and yogurt. Stay away from anything acidic or fizzy, which can irritate the mouth sores.
How long you are contagious
People are most contagious when they first experience symptoms. Once the fever is gone for 24 hours, the mouth sores are mostly resolved and the rash is starting to heal, children can go back to school — that can take anywhere from a few days to a week.
“I would not be cavalier about it and send your child to school sick,” Handy said, adding: “If they are past those acute symptoms, they are then at the point where they have a lower likelihood of spreading.”
However, people can continue to shed enterovirus in their stool for several weeks after they are no longer symptomatic, so some risk of transmission remains. Because of this, it is important to practise good hand hygiene and disinfect contaminated objects.
Words of warning
In very rare cases, enteroviruses can cause encephalitis or meningitis — inflammation of the brain or tissues and fluid that surround it. This risk appears to be greatest in infants. Signs to watch out for are high fever and severe headache; in babies, this may show up as extreme irritability, or it may be difficult to rouse them. If this happens, take your child to a hospital right away.
“I don’t want to alarm any of the readers or the public, but just like any virus,” sometimes there are certain rare strains that can cause complications, Whitley-Williams said.
— Flu
Sore throat, congestion, fever, aches — all of which come on suddenly. Contagious for about five days. The seasonal flu is caused by two types of influenza viruses: A and B. Both can be circulating simultaneously, but typically one subtype dominates each flu season.
It is often not easy to tell whether you have the flu versus another respiratory virus, but you can get tested at a pharmacy or doctor’s office. At-home rapid flu tests are available in other countries but not in the United States, though experts hope they will be eventually.
Symptoms
Flu symptoms include sore throat, runny nose, congestion and cough, as well as fatigue, fever, headache and muscle aches. Some people also experience vomiting or diarrhea.
The clearest indicator that you have the flu might be how bad you feel and how quickly that misery comes on — a common analogy is that it feels as if you’ve been hit by a truck.
“If you feel much sicker than you have with other colds, then be thinking about flu,” Ray said. People typically feel the worst during their first three days of illness and then symptoms start to taper off, resolving after about a week.
How it’s spread
Influenza is primarily spread through respiratory droplets — the mucus and saliva that are dispersed by coughing, sneezing or talking. The virus is also present in smaller aerosol particles that stay suspended in the air, though experts say you are less likely to get infected from aerosols alone. Influenza can be transmitted by droplets that land on objects and surfaces, too, where the virus remains infectious for many hours.
While all modes of infection are possible, “it is probably driven by close-range transmission,” said Seema Lakdawala, an associate professor of microbiology and immunology at Emory University School of Medicine. If you are near an infected person, she said, “you are inhaling small aerosols, large aerosols and potentially touching things that are contaminated in that space.” Putting a mask on the sick person reduces the risk that they will infect others. Once you are infected, it usually takes two to four days until symptoms emerge.
How it’s treated
Your best weapon against the flu is getting an annual flu shot, which significantly reduces the risk of a severe infection.
There are also antiviral treatments, such as Tamiflu, that can help minimize symptoms. These medications need to be taken in the first few days of the illness, so it’s essential to get tested and treated early. Home remedies and over-the-counter medications can also help with symptom relief, but take a close look at the labels — an advisory committee to the FDA recently said that phenylephrine, a common decongestant ingredient, is ineffective.
How long you are contagious
Experts say five days is a reasonable estimate for how long someone is contagious with the flu. Most people begin shedding virus the day before they start feeling sick, and they are most contagious during the first three days of symptoms. Virus levels drop as symptoms begin to abate.
“If I got flu Monday, by Friday I am probably not very infectious for others,” Walsh said.
After that, Lakdawala said, “if you are starting to feel better, you’ll probably not have as much virus in your nose,” and it is fine to go out in the community. However, she added, if you have lingering symptoms, or if you are going to see someone who is at high risk for severe infection (for instance, if the person is over 65 or has a preexisting condition), you should wait another few days or wear a mask.
You may still be coughing at that point because of lingering inflammation in the airways. That late-stage cough is unlikely to be contagious, but you should continue to wash your hands frequently and cover your mouth when you cough, just in case.
Words of warning
One of the primary concerns with influenza, and one of the main causes of influenza-related death, is pneumonia. Signs that you may have pneumonia and should seek medical attention are shortness of breath, pain when you breathe, coughing up very dark mucus and coughing attacks so severe that they cause you to vomit.
— Conjunctivitis (Pink Eye)
Itchy, red, weepy eyes. Highly contagious for a few days to a couple weeks, if you get it in both eyes.
Conjunctivitis, or pink eye, is a general term that means inflammation of the conjunctiva — the mucus membrane that lines the skin around your eyeball. It is most often caused by viruses in the adenovirus family. There are bacterial forms of conjunctivitis, too, but those are less common.
Symptoms
The symptoms of conjunctivitis are itchy, red and weepy eyes; they typically last two to seven days (bacterial conjunctivitis resolves faster than viral). Adenovirus can spread from one eye to the other, so it’s possible to have pink eye for two weeks.
“Bacterial conjunctivitis, more classically, is just one eye,” Handy said. “Viral conjunctivitis, more classically, is both eyes because it’s so contagious that it’s hard to protect one eye from the other.”
How it’s spread
Conjunctivitis caused by adenovirus spreads extremely easily. It’s transmitted by viral particles that get onto your finger, typically picked up from surfaces, and then spread to your eyes when you rub them.
How to treat it
If you think you or your child have pink eye, see a doctor to find out which type it is. “This is one infection where I do really advocate for talking with your health care provider,” Handy said, “because the counseling is very different based on what type you have, as is the treatment.”
There is no treatment to get rid of viral conjunctivitis, and it will eventually resolve on its own. In the meantime, you can use damp compresses to help with symptoms. Bacterial conjunctivitis is treatable with antibiotic ointment or drops.
How long you’re contagious
As long as you have symptoms of viral conjunctivitis, you’re contagious; that can be anywhere from a few days to a couple weeks, depending on if you get it in both eyes.
The best way to prevent spreading it to others is to stay home from work or school until your symptoms are gone. If the infection lingers for weeks, talk to your doctor about whether there are ways to safely go out in public. At the very least, do not touch your eyes, and be diligent about hand washing — that means frequent lathering with soap and water (adenoviruses are so hearty that hand sanitizer won’t cut it).
Adenoviruses can also live on surfaces for several weeks, so disinfecting contaminated objects (like eyeglasses) and high-touch surfaces (like light switches) is essential.
“It’s very, very contagious,” Schaffner said. “You rely on isolation until you get better — and hand washing.”
Bacterial conjunctivitis is less common, less contagious and more treatable. People are usually no longer infectious a day or two after starting antibiotics.
— COVID-19
Congestion, fatigue, cough, sore throat. Most contagious through Day 5.
By now, most of us are all too familiar with COVID, which is caused by the SARS-CoV-2 coronavirus. While the virus has evolved since the early days of the pandemic, how it spreads and the symptoms it causes have largely remained the same.
Symptoms
The most common COVID symptoms are sore throat, congestion, fatigue, fever and cough, which can make it hard to distinguish from other respiratory viruses.
Rapid tests are still the easiest way to determine if what you have is COVID. If you test negative on the first try, swab yourself again 48 hours later because you may not have had enough virus in your nose initially for a rapid test to detect the infection. PCR tests are more precise, but they are more expensive and less convenient because you have to go to a doctor’s office or pharmacy to receive one.
Symptoms resolve within a week for most people, but some can have protracted infections that linger for weeks or even develop into long COVID.
How it’s spread
More than any other respiratory virus on this list, COVID is spread by tiny airborne particles.
“Every time you take a breath, your virus is going out into the room, and it sort of hangs there,” Walsh said. “People can walk by and inhale it and get infected.”
It is also transmitted in larger respiratory droplets that are expelled when you cough or sneeze. However, the virus does not appear to spread very well via surfaces, so becoming infected by touching a contaminated object and then touching your face is less of a concern.
Once infected, it takes about two to four days for symptoms to develop.
How it’s treated
Taking the antiviral drug Paxlovid within the first five days of an infection can reduce the risk of severe disease. The vaccines are also very effective at preventing hospitalization and death. For relief from mild symptoms, over-the-counter medications for cold and flu may help.
How long you’re contagious
Guidance from the Centers for Disease Control and Prevention says that people can go out in public after their fifth day of symptoms, as long as they are fever-free. However, people should continue masking for another five days to minimize the risk of spreading the virus to others.
Experts say this is generally good advice. For most people, “COVID is no longer infectious in the second week,” Ray said. “But the variability is still there.”
For example, if you have a moderate or severe case of COVID, in which you are experiencing shortness of breath or have to go to the hospital, you should isolate for 10 days. “The more severe the infection, the more protracted the infectiousness,” Ray said.
Some people continue to test positive on rapid tests after Day 5, but research suggests that most are no longer contagious at that point because the virus has stopped replicating. To be safe, follow the guidance from the CDC and continue to mask in public for Days 6 through 10.
Words of warning
The risk of hospitalization and death from an acute case of COVID has diminished significantly since the beginning of the pandemic because nearly everyone has antibodies to the virus now, thanks to vaccines, a prior infection or both. But for older adults, people with preexisting conditions like heart disease and diabetes and people who are immunocompromised, some risk remains. There is also the concern of longer-term health consequences, including long COVID and cardiovascular complications, after the immediate infection resolves.
— Strep Throat
Very sore throat, maybe fever. No longer contagious 24 hours after starting antibiotics.
Strep throat is the odd one out in this list of diseases because it’s caused by a bacteria: Group A streptococcus. Close to 100 strains of Group A streptococcus exist and they can result in several diseases, including scarlet fever, rheumatic fever and skin infections, but strep throat is the most common.
Symptoms
The characteristic symptom of strep throat is, of course, a very sore throat. You might also see a white film in the back of the infected person’s throat. Some people develop a fever, too.
Many infections can cause a sore throat — what distinguishes strep throat is that it isn’t accompanied by other common respiratory symptoms, like a runny nose or cough. The only way to know for certain if you have it is to be tested by a doctor using a throat swab.
How it’s spread
Strep throat is transmitted through close personal contact with an infected person, primarily in the form of respiratory droplets. That means what’s coming out of their nose and mouth goes into yours.
Strep throat doesn’t appear to spread very well via objects. One study conducted in the 1950s among military recruits found that people who used blankets contaminated with streptococcus bacteria were no more likely to develop strep throat than those who received clean blankets.
“The inanimate environment plays a minor role in the transmission of Group A strep,” Schaffner said. “It’s all close personal contact.”
It typically takes about 48 hours after an exposure until symptoms develop.
How it is treated
If you think that you have strep throat, get tested immediately because the disease can be treated quickly and easily with antibiotics, like penicillin or amoxicillin.
“Pretty much every patient who is diagnosed with strep throat should be treated with a course of antibiotics,” said Dr. Stanford Shulman, an emeritus professor of pediatrics at Northwestern University Feinberg School of Medicine.
How long you are contagious
Once antibiotics are started, the bacteria die off quickly, and within roughly 24 hours the person is no longer contagious. As a result, the experts say that children can go back to school a day after they begin medication. They might still have a mild sore throat, but there is no risk to others.
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“Most kids can return to school within that next 12 to 24 hours, as long as they’re otherwise doing well: fever-free, eating and drinking OK,” Handy said.
Words of warning
In addition to reducing the risk of transmission, it’s also critical to treat strep throat because the bacteria can cause other, more severe infections. Those include skin infections known as cellulitis and impetigo, as well as scarlet fever and rheumatic fever, where the immune system starts attacking the heart valve. In the most severe — and rare — cases, streptococcus bacteria can cause a blood infection, bone infection, septic shock or necrotizing fasciitis — a flesh-eating infection.
It’s important to know about these more severe manifestations “not to scare parents,” Handy said, but to make sure they get their children treated, and, “if symptoms worsen, they get medical attention quickly.”
This article originally appeared in The New York Times.