Can you get COVID-19 again? We answered some common coronavirus questions.

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This post has been updated. It was originally published on 04/17/20.

Since the novel coronavirus began spreading throughout China in January 2020, it has reached 219 countries and infected over 100 million people globally. So far, over 2 million people have reportedly died from COVID-19. To contain community outbreaks, countries have taken drastic measures like travel restrictions and country-wide mask mandates.

Amid widespread panic, online misinformation has thrived—websites have claimed that hot baths and hand dryers can kill the virus. Some people have even placed face masks on their dogs, despite the fact that pets like cats and dogs likely can’t spread the virus to humans.

Part of the reason for this confusion is that the coronavirus currently circulating around the world is novel; even a year into the pandemic, there’s still a lot that experts are still figuring out.

“We all wish that we had the answers, but in infectious disease epidemiology we are accustomed to operating in this uncertain space,” says Caitlin Rivers, an epidemiologist at the Johns Hopkins Center for Health Security. She has previously studied infectious diseases like Ebola and MERS, all of which she says present similar challenges early on when definitive information is scarce; with any new virus, thorough scientific investigations take time. “It probably seems frustrating to readers, but this is one of the challenges of facing a new pathogen.”

Here are some of the most common questions we’ve been getting and what Rivers, and others, have to offer.

How do I know if I have the COVID-19 infection?

This illness usually looks like a common cold. Anytime between about two and 14 days after exposure, people usually get a fever and cough. People may also experience shortness of breath, Rivers says, though it probably doesn’t occur with most mild infections.

You should call your doctor if you develop symptoms after having close contact with an infected individual or visiting any area with ongoing community spread, according to the CDC.

Who is the most susceptible to infection?

The most common route people have caught the novel virus is through close contact (which is defined as anything 6 feet away or less) and droplets from the nose or mouth, Rivers says.

When infected, the demographics most at risk of severe illness are older adults and individuals with serious chronic medical conditions like heart disease, diabetes, and lung disease, according to the CDC.

Around 22.5 percent of US cases are in young adults aged 18-29, with another 20.6 percent in older adults between 50 and 64, according to the CDC. Less than one percent are in children 0-4, and less than 10 percent are in children 5-17. And while only 4.1 percent of the cases are in age group 75-84, deaths shoot up to 27.6 percent for this same age range. Elderly people 85 and up make up around a third of COVID-19 deaths in the US but only account for less than three percent of total case counts.

Female patients make up slightly higher case counts, but male patients make up 54.1 percent of COVID-19 related deaths in the US.

How long are people contagious for?

People with a COVID-19 infection are likely to be contaigous for around nine days, but are most contaigous for the first five days of infection, according to a Lancet study from November. COVID-19 antibodies—which help people fight off the infection—develop to a detectable level two or three weeks after infection, according to the Mayo Clinic, which is why antibody tests can be ineffective at showing if you are sick at this very moment. Researchers still don’t know what level of immune response is sufficient, Rivers says.

COVID-19 spreads most easily through close contact when people are at their sickest—though asymptomatic individuals can still infect others, the CDC reported. A severely sick person is likely infectious for up to 20 days past infection, whereas an asymptomatic, mild, or moderate patient is likely contagious for no longer than 10 days post-infection.

[Related: Here’s where all the COVID-19 vaccine candidates currently stand]

Where did the virus originate from?

The SARS-CoV-2 virus first appeared in Wuhan, China in late December 2019. The specific source is currently unknown, though many of the first COVID-19 patients had visited a fish and wild animal market. Most researchers now believe that the disease began in bats, but are not sure how it jumped to people.

Pinpointing the origin could be important to avoiding high-risk situations in the future, Rivers says. A November WHO report found no evidence of SARS-CoV-2 in sampled frozen animal carcasses from the wet market in question, but sewage samples did.

How does it actually get into my body?

The SARS-CoV-2 virus most commonly enters the body through droplets from the nose and mouth from person to person via coughing, sneezing, or talking. The best way to protect yourself from catching the virus is to stay six feet away from people whenever you’re in public, wear a mask as often as you can outside your home, and wash your hands often.

How does the novel coronavirus affect children?

Most infected children presented mild cold-like symptoms, which may contribute to underdiagnosis in youths. Yet kids can still contract and spread the virus to more vulnerable populations. Some recent studies have shown that despite having less severe symptoms, they tended to have the same amount of the virus in their upper respiratory tracts as infected adults. Luckily, however, schools do not tend to be superspreaders even if there is some spread of COVID-19.

“The fear that you’d have one infected kid come to school,” Sally Permar, a professor of pediatrics and immunology at Duke told the AAMC, “and then you’d have many other kids and teachers and relatives [at home] get infected — that hasn’t happened.”

Can pets spread COVID-19?

Your pet very likely can’t infect you with the virus—though they can catch it and test positive for weak levels of the novel virus, according to Hong Kong’s Agriculture, Fisheries, and Conservation Department. A Pomeranian living in Hong Kong may have caught the disease from its owner, though it didn’t show any symptoms.

There is no evidence that dogs play a role in the spread of this human disease or that they can become sick, the World Organization for Animal Health said. Pet owners should practice basic hygiene measures like “hand washing before and after being around or handling animals, their food, or supplies, as well as avoiding kissing, licking, or sharing food.”

Can it be transferred through food and drink?

Though there’s currently no definitive evidence, infected people who handle food could possibly pass on the virus (it’s been found in people’s stool and can spread through droplets from the nose or mouth). Yet the cooking process may kill the virus, infectious disease specialist Todd Ellerin said in a blog post.

Can you get COVID-19 more than once?

Yes, but it is still a bit of a mystery as to who gets reinfected and how often it occurs. This is because immune responses can wane in some people, meaning that even if you’ve built up a defense against the virus once it doesn’t mean that defense lasts forever. Reinfection happens when you’ve been sick with one strain, and then become reinfected with a different strain, which can raise alarms when it comes to lasting immunity. Countries like Brazil, Sweden, Mexico, and Qatar have seen at least 95 suspected reinfections as of November, and it’s still not clear if second cases tend to be milder or more severe than first infections. In the US, particularly, tracking and investigating suspected cases of reinfection is Iimited.

A second case of COVID-19 is different from long-haul COVID-19, which are the long-term impacts of having the illness.

How long does the coronavirus live on surfaces?

Research suggests that the virus can persist in the air for about three hours and remain on some surfaces, like plastic and stainless steel, for up to two to three days. The timing seems to depend on the specific material, with shorter detection periods on cardboard (up to 24 hours) and copper (up to four hours). Solutions that contain diluted bleach or other ingredients like ethanol, hydrogen peroxide or quaternary ammonium could effectively disinfect surfaces. Nevertheless, you’re much more likely to catch or spread COVID-19 through other people than from a surface.

“In my opinion, the chance of transmission through inanimate surfaces is very small,” wrote Emanuel Goldman, professor of microbiology, biochemistry, and molecular genetics at the New Jersey Medical School of Rutgers University in the Lancet, “and only in instances where an infected person coughs or sneezes on the surface, and someone else touches that surface soon after the cough or sneeze (within 1–2 h).”

For now, the CDC recommends disinfecting surfaces to lower the possible risk of infection.

Can I become infected when taking public transportation?

As mentioned above, the virus’ effect on surfaces, including stainless steel poles and plastic or fabric seats, is still unclear. However, it can definitely spread through droplets from the nose or mouth so standing on a packed train during rush hour could therefore pose a risk, particularly on longer commutes: Close contact (less than 6 feet apart) for at least 15 minutes with an infected person likely spreads COVID-19.

Currently, public transit authorities around the world are taking precautions like disinfecting vehicles and adjusting ventilation to prevent transmission, though it’s unclear whether these measures are effective.

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Does the flu shot protect me?

There’s no direct advantage, Rivers says, because coinfection of both the flu and COVID-19 doesn’t appear to be common. Still, fewer flu patients could significantly lessen the burden on health care providers.

What should I do if soap and hand sanitizer are sold out?

As cleaning supplies fly off the shelves, some stores have rationed hand sanitizer and soap—which are extremely helpful in preventing COVID-19 infections. Though professionally manufactured products are ideal, it’s possible to make your own hand sanitizer until you can buy more if your store is out.

Should I shave my beard to avoid infection?

Shaven or unshaven, beards probably have nothing to do with the disease’s spread. Last month, online misinformation led users to believe that the CDC recommended certain beard shapes over others to avoid COVID-19. The popular poster was not produced in relation to the novel coronavirus outbreak, but rather intended for professionals who require respiratory protection at work.

Still, everyone should wear masks when outside of your home, and even consider doubling up if you feel the need.

[Related: On surviving—and leaving—prison during a pandemic]

Can it spread through feces?

Even after people stop showing symptoms, traces of the virus can appear in their feces. You are far more likely to acquire or spread the virus through close contact and droplets, but it is theoretically possible to be exposed to SARS-CoV-2 by breathing aerosolized fecal matter after using a public toilet or by ingesting the virus through contact with a contaminated surface. Just another important reminder to wear your mask and wash your hands frequently.

Can handling cash give me COVID-19?

We still don’t really know how long the virus stays on surfaces and whether lingering residue can actually infect people. If you’re worried, perhaps switch to credit cards or Apple Pay (make sure to regularly disinfect your phone and your cards). And, as always, wash your hands.

Correction: This article has been updated to reflect the fact that staying within 6 feet of an infected person (not about 6 feet away from them) can increase someone’s chances of getting the virus.