HOW CAN YOU BE INFECTED WITH TWO VIRUSES?
The same way you can be infected with just one virus: exposure.
If a person is in a place where viruses are circulating — that is, in any place where other people are present — then two or more viruses can cause infection at the same time.
Ideally, someone who feels sick is able to stay home, reducing the risk of becoming infected with a second virus. But viruses have incubation periods, multiplying for a day or more inside the body before the person starts to feel sick. So it is easy for someone to pick up more than one bug before feeling sick enough to retreat to the bedroom, Cherry said.
COVID in particular has a long presymptomatic period, up to four days, though the omicron variant of the virus seems to come on faster. If you're out in a lot in crowds, a double whammy with flu is certainly possible.
"If you're out doing things without a mask, then you're more likely probably to get both," she said.
These respiratory viruses commonly enter through the nasal passages. Often, they are trapped safely in mucus, which is then swallowed and dissolved harmlessly in the stomach. But when they manage to latch on to cells in the airways, the viruses penetrate the cell membrane, hijack its inner machinery, and begin to copy themselves — the definition of an infection.
Flu viruses latch onto substances on the cell surface called sialic acids. The coronavirus, on the other hand, latches onto a "receptor" called ACE-2. Though they may be infecting cells in the same part of the body, neither is likely to fully crowd out the other, Cherry said. Generally, there is plenty of real estate to go around.
WILL COINFECTIONS MAKE YOU SICKER?
It depends on the timing. If the person is lucky, the immune response to the first invader could help protect against the second, Cherry said.