Flu and Covid at the Same Time? Your 'Flurona' Questions, Answered

Reports about dual infection with the flu virus and the coronavirus have been making sensational headlines recently. Last week Israel confirmed its first case of “flurona,” in an unvaccinated woman, followed by a growing number of cases in children in the United States. None were seriously ill, but the name “flurona” stuck.

“It sounds like ‘sharknado,’” Dr. Saad B. Omer, the director of the Yale Institute for Global Health, said. “But it’s not a known medical term.”

As flu season sets in and the Omicron variant continues to surge, how worried should we be? We spoke to experts to better understand what it could mean to test positive for both infections. Here’s what we learned.

Why am I just hearing about this now?

People have been testing positive for both Covid-19 and influenza, or flu, since the pandemic began.

From late January to late March 2020, researchers in China found almost 100 cases of patients testing positive for both illnesses in Wuhan. The Atlantic reported on a family in Queens that tested positive for both infections that February. And researchers in Barcelona published a paper in May 2020 describing four people with both illnesses in the early months of the pandemic.

At the time, before vaccines were available, such dual infections, or what infectious disease experts call co-infections, appeared to be uncommon. A spring 2020 study in New York City, for instance, found that after about 1,200 Covid-19 patients were tested for other respiratory viruses, such as those causing influenza or the common cold, just 36, or less than 3 percent, had simultaneous infections. Last winter was also a notably subdued cold and flu season, with fewer people socializing and many wearing masks.

“The reason we haven’t talked about it much is that it’s not been clinically a challenge yet,” said Dr. Jonathan D. Grein, an infectious disease physician and the director of hospital epidemiology at Cedars Sinai Medical Center. “We anticipate that as flu becomes more prevalent, we will see more co-infections.” If it becomes a serious problem, experts expect to know a lot more about it in the coming months.

Will co-infection make me twice as sick?

A co-infection doesn’t immediately mean that a patient will be doubly sick. A strong immune response may actually help the body fight off pathogens of all types, so one infection could stimulate some additional protection.

“An infection to one might help to aid your immune response to another,” Dr. Grein said, “because it’s activating that same immune response that’s going to be effective in fighting both.”

Still, scientists don’t know for sure yet, because so few people have tested positive for both Covid-19 and influenza. But judging from past trends, doctors are not overly worried.

“The majority of people who have influenza do just fine. The majority of people who have Covid do just fine, especially if they’re vaccinated,” said Dr. Andrew D. Badley, an infectious disease specialist and the chair of the SARS-CoV-2 Covid-19 Task Force at the Mayo Clinic. “It is hard to predict,” he continued, “but we expect that the majority of people who are co-infected with the two viruses will also do just fine.”

But as Dr. Badley and other experts pointed out, it’s generally better to have one infection rather than two. There’s more chance for complications with two infections, and it’s a bigger strain on the body.

“The human immune system can create antibodies for multiple pathogens simultaneously,” said Dr. Andrew Noymer, an epidemiologist and associate professor of population health and disease prevention at the University of California, Irvine, who studies influenza.

“But given the choice between being infected with one or two, I would always choose one,” he continued, adding, “I can’t tell you that two is so much worse than one, but the less viral threats, the better.”

Who is most susceptible?

Dr. Omer, who is also a professor of infectious disease and epidemiology at Yale, identified two groups he thought could be most susceptible to co-infection.

First: unvaccinated adults. “Based on previous work on vaccinations, people who refuse one vaccine might refuse others as well,” he said. He said he expected there to be a “significant overlap between people who refuse both vaccines.”

Second: children, especially those under 5, who are too young to get vaccinated against Covid-19. Kids are also petri dishes, as any parent will tell you, and have lived through fewer cycles of the flu. So even if a child got a flu shot, Dr. Omer said, “their library of protection is narrow” against the many viral flu strains that can emerge each year.

What are the risks for the frail or elderly?

Experts agreed that a patient who is already vulnerable to severe disease from one illness may suffer even more if doubly infected.

“It is probable that those people who would have had a bad outcome from flu will have a very bad outcome from the combination of flu and Covid,” Dr. Badley said.

What are the risks for children?

Pediatricians were optimistic that “flurona” would not overwhelm most children. That’s because kids may be more likely than adults to get multiple infections at the same time.

“It’s not that surprising to most of the people who work in pediatrics,” said Dr. Frank Esper, a pediatric infectious disease physician at Cleveland Clinic Children’s Hospital. “We see co-infections all the time.”

“Co-infections with coronavirus are expected,” Dr. Esper continued. “I do not find it to be alarming.” His research team has found that co-infections with a variety of respiratory viruses are more common in children than adults. Other earlier studies likewise suggest that infection with two concurrent viruses do not make a child sicker, he said.

Dr. Aaron M. Milstone, a professor of pediatric infectious disease at the Johns Hopkins University School of Medicine, also said he was cautiously optimistic. Just because a child has two viruses, he said, “doesn’t mean that the immune response will be twice as aggressive or generate twice as many symptoms.”

“Because the viruses have been co-circulating, it is very reassuring — especially for parents — that we have not seen a lot of children coming into the hospital with severe co-infections,” Dr. Milstone said. He added, “We’re not all of a sudden seeing more kids in the intensive care unit.”

What if I test positive for both viruses?

First and foremost: Don’t panic. It may be extra stressful, but that doesn’t mean you’re about to get extra sick. Also, it’s possible that you may have already had one virus and recovered from it, but that it’s still showing up in your test results.

If your symptoms are serious, or you have trouble breathing, call your doctor. Doctors said they would probably treat a patient who had both infections similarly to the way they would treat someone who had just one. Experts do not believe the treatments would work against each other or cause problems in the patient’s body.

“The decision to treat for Covid has to do with how sick you are,” Dr. Badley said. “That would not change if you had flu at the same time. What might change is that you might also get therapies that are directed toward influenza.”

How can I prevent co-infection?

On this one, the medical advice remains consistent: Get vaccinated for both Covid and flu. And get vaccinated right now.

Both kids and adults can get both vaccines at the same time. Children ages 5 years and older are eligible for a Covid-19 vaccine, and children older than 6 months can get vaccinated against the flu.

“We have given multiple vaccines at the same time for decades,” Dr. Badley said, with no ill effects. “The side effects are the same” when administered together, “and the side effects for both vaccines are very, very low.”

In addition, experts agree you should wear masks and maintain social distancing measures when appropriate. Both flu and the coronavirus are airborne viruses, so limiting your exposure cuts down on your chances of getting infected.

“If you don’t want to get the coronavirus, and you don’t want to get flu,” Dr. Esper said, “the best thing you could do is: Do basically everything you did last year.”