As the coronavirus pandemic surges to record highs across the country, flu season is off to an unusually slow start. Usually around mid-November , the flu has a solid footing in the Northern Hemisphere, but right now were only seeing a handful of scattered influenza outbreaks. Experts predicted and hoped this may happen thanks to the measures many are taking to fight COVID-19 .

But this doesnt mean the threat of twindemic is behind us. The flu usually doesnt peak until around February, so theres still plenty of time for the virus to gain momentum in the nation and converge with COVID-19.

As infectious disease experts have warned, a twindemic would put even more pressure on our already distressed health care system. A substantial portion of the population could get sick with both infections within weeks or months of one another, and some very unlucky people could contract both infections at the same time.

Already, a handful of people in the U.S., U.K. and China have been co-infected with the coronavirus and influenza. Though data is limited in how the viruses interact with each other and together affect the body, early evidence suggests those who contract both have a rougher go of it.

How someone could contract both viruses simultaneously

The first thing to know about a coronavirus-influenza co-infection is that its possible because the two viruses bind to different parts of the body. They arent competing with each other when it comes to infecting our cells.

Some evidence on influenza co-infections suggests a short window exists in which one viral infection could inhibit a second viral infection from successfully fusing with our cells, according to Dean Winslow , an infectious disease specialist with Stanford Health Care. But that window is very short and unpredictable, Winslow told HuffPost.

So while some people may bypass a co-infection if the timing is just right, others may not be so lucky. Winslow said its also unclear if that protection exists only between influenza strains or if it holds up with other viruses like the coronavirus.

Co-infections often lead to worse outcomes

The general belief is that a COVID-19 and influenza co-infection could be devastating.

Matthew Heinz , an internist treating COVID-19 patients in Tucson, Arizona, said hes treated numerous patients whove had co-infections with the flu and other common coronaviruses in the past.

They look worse, they sound worse, they take longer to recover, Heinz told HuffPost.

Early data suggests the same is true with COVID-19. A study from the U.K. found that co-infected people typically had bleaker outcomes. Those co-infected had a doubled risk of dying compared with patients infected solely with COVID-19 (and nearly six times greater mortality risk compared with those with neither infection). They were also more likely to be admitted to the intensive care unit and require a ventilator. Researchers in China and Iran have published similar findings.

Influenza can harm the body similarly to COVID-19 both cause decreased blood oxygen levels, respiratory issues and inflammation.

Really all strains of influenza and SARS-CoV-2 are potentially very, very lethal infections, Winslow said. Having [these] two infections at the same time could potentially make the inflammatory response much worse.

The risk is expected to be greater among people more susceptible to each virus such as older adults and people with underlying health conditions like obesity, cancer and lung disease.

Those vulnerable groups overlap between both illnesses, which puts them at an even higher risk, said Onyema Ogbuagu , a Yale Medicine infectious disease doctor.