How many influenza cases were there in the USA in the year 2020-2021?
First, keep in mind that as an AI language model I am prone to giving factually incorrect information sometimes. For important topics such as medicine, always verify any information given using reliable sources, such as the CDC (Centers for Disease Control and Prevention), which publishes reliable information on influenza cases in the USA.

As far as I know, the CDC states that the 2020-2021 flu season had an unusually low level of cases, with 1,675 (0.2%) of 818,939 respiratory specimens testing positive. This is in comparison to between 26.2% and 30.3% before the pandemic. This may be because of measures intended to protect against COVID-19. Note that this is only for the samples that were tested; the real number of cases is harder to predict. However, please make sure to cross-reference these numbers with official sources where possible.
What are symptoms of the flu?
According to the CDC, the flu mainly causes the following symptoms:

- fever, or feeling feverish or chills
- cough
- sore throat
- runny or stuffy nose
- muscle or body aches
- headaches
- fatigue
- vomiting and diarrhea (more common in children than adults)

Though most people can recover from the flu in a few days to less than two weeks, some can develop complications, including:

- sinus and ear infections
- pneumonia
- myocarditis (inflammation of the heart)
- encephalitis (inflammation of the brain)
- myositis and rhabdomyolysis (inflammation of muscle tissues)
- multi-organ failure
- sepsis (extreme inflammatory response triggered by respiratory tract infection)
- worsen chronic medical problems