The New York Times has made a free e-book with answers your coronavirus questions. It features more than two dozen chapters on how you can reduce your risk, what you can do to protect others, what scientists have learned, what to do if you’re worried about the stock market and more. You can download it on Apple Books and elsewhere. Below is an excerpt.

With the spread of the coronavirus comes another ailment: anxiety about every single symptom. Is your nose feeling itchy because you’re trying not to touch your face, because you picked up the flu — or is it, just maybe, the coronavirus?

With the start of spring, allergies may be triggering symptoms that can make it difficult to determine what your body is trying to fight off. Dr. Amesh Adalja, an infectious disease specialist at the Johns Hopkins Center for Health Security, helps explain the subtle differences between signs of allergies or infection with the flu or the coronavirus.

What are your symptoms?

First, consider the time of year. Allergies and influenza tend to be seasonal. If you have a runny nose in the spring and this happens every year, allergies are the likeliest culprit. If it’s winter and flu is raging in your community, then that’s the probable explanation. The flu is far more widespread than the coronavirus.

But flulike symptoms in warming weather — in a place with documented coronavirus transmission? Maybe it’s not the flu.

Influenza dies back in the summer, but scientists have yet to see evidence that the coronavirus will go away as temperatures rise. Coronavirus infections have been spreading in equatorial climates like Singapore’s and in the Southern Hemisphere, now in the middle of summer.

Consider, too, where the symptoms first started appearing. “It’s usually your nose and eyes where you develop symptoms of seasonal allergies,” Dr. Adalja said.

The seasonal flu, on the other hand, is more likely to affect your whole body, as is the case for many other respiratory viruses — including the coronavirus. So if you experience fevers, headaches or muscle aches, consider flu or coronavirus.

“There’s a feeling of overall malaise that is associated with viral infections,” Dr. Adalja said. Except for seasonality, it can be hard to tell the two apart.

“Unfortunately, there’s no reliable way to distinguish between early symptoms of the flu and coronavirus,” Dr. Adalja said. “The only way to distinguish the two clinically is with a diagnostic test.”

According to reports from nearly 56,000 laboratory-confirmed cases in China, people infected with the coronavirus develop symptoms like a dry cough, shortness of breath and a sore throat, in addition to fever and aches.

Around 5 percent of patients may also experience nausea or vomiting, while roughly 4 percent develop diarrhea. Researchers are not sure why some people develop gastrointestinal symptoms with coronavirus infections.

“But that’s not something you usually see with influenza in adults,” Dr. Adalja said.

Severe coronavirus infections can result in lung lesions and pneumonia. But the vast majority of those infected get only mild cases that often resemble the flu.

Your personal history can give doctors clues to what’s going on. If you traveled to an area with large clusters of coronavirus cases, or were in contact with someone who later tested positive for the virus, you may have caught it, too.

Doctors and health care workers have to work with these possibilities because tests are still available only in limited quantities in the United States, Dr. Adalja said.

How bad is it?

Pay close attention to whether your symptoms worsen over time. Discomfort due to allergy remains consistent until you treat it or the allergen goes away. Symptoms of the flu tend to resolve in about a week.

The new coronavirus, on the other hand, seems to cause more severe symptoms than the average seasonal flu and seems to have a higher fatality rate, although the numbers are a bit uncertain.

If you are elderly or have other health conditions, such as heart disease, Type 2 diabetes or immunodeficiency, you are more vulnerable to viral infections and are more likely to develop severe disease if infected with the coronavirus.

Early estimates from China show that the average death rate among coronavirus patients is around 2 percent, but that figure rises to 8 percent in people 70 years or older, and about 15 percent in people 80 years or older.

But nobody is certain how many cases are very mild or asymptomatic.

What to expect

The general advice for people who get sick with the flu or coronavirus is very similar: Rest and drink plenty of fluids.

Mild cases of the flu resolve by themselves within a few days. Although coronavirus infections tend to last a little longer, most people with mild cases get better in about two weeks, Dr. Adalja said.

Severe cases may take three to six weeks to resolve. Doctors can only give supportive care, providing patients with intravenous fluids, medicines to keep the fever down or oxygen to help with breathing.

There are no approved treatments for coronavirus infections, although a few clinical trials are underway that test antiviral drugs such as remdesivir.

It’s up to you to take precautions to prevent a coronavirus infection, and to take stock of your medical and travel history. But you don’t need to go to the doctor for every sniffle or scratchy throat.

“You should be going to the doctor for something that would trigger concern, even before you had heard of the coronavirus,” Dr. Adalja said.

“So if you’re somebody that’s elderly or somebody that has another medical condition, if you develop shortness of breath, if you develop extreme fatigue, those are real indicators to call your physician and go to the hospital.”