Seasonal viruses can be uncomfortable and annoying, but they’re rarely dangerous. Influenza, on the other hand, has the potential to become quite serious, particularly in the very young, the elderly and individuals with underlying respiratory disease. For this reason, it’s important to know which symptoms of seasonal viruses are flu-like, such that these viruses can be monitored and reported to a physician should they become more serious.
Fever
Flu.gov notes that one hallmark symptom of true influenza is high fever, often accompanied by headache. Unlike many other seasonal viruses, flu headache and fever come on quickly, and the fever can get quite high—up to 101 degrees Fahrenheit in adults, and as high as 105 degrees Fahrenheit in children. Fever can result in other symptoms as well, including pain behind the eyes and light sensitivity. Seasonal viruses in which a sudden fever and headache occur as symptoms are certainly flu-like in their presentation, and bear watching closely.
Muscle Aches
As the immune system kicks into action, immune cells release inflammatory chemicals that help make the body less attractive to pathogenic invaders. This inflammatory response certainly assists in clearing up a viral infection, but it can be associated with some uncomfortable side effects. The Mayo Clinic, for instance, notes that flu and flu-like viruses often cause muscle aches, joint pain and lower back pain.
Respiratory Symptoms
Both flu and flu-like viruses can cause respiratory symptoms, according to the U.S. Centers for Disease Control and Prevention, or CDC. These symptoms can include a dry or productive cough, runny or stuffy nose and sore throat. Particularly with a fever, it’s easy for individuals suffering from seasonal flu-like viruses to become dehydrated. This exacerbates respiratory symptoms—even, surprisingly, runny nose—so staying well hydrated with clear fluid is one way to reduce symptoms of flu-like viruses.
Gastrointestinal Symptoms
The CDC also notes that it’s possible to experience gastrointestinal upset leading to nausea, diarrhea and vomiting with flu and flu-like viruses. It’s worth noting that the word “flu” is quite frequently misused with regard to seasonal viruses—only illnesses caused by the influenza pathogen are technically the flu. Flu-like viruses include pertussis and colds, and are not true “flu.” Further, the gastrointestinal upset common to adults who have managed to insult the gut that is frequently called “stomach flu” is not actually a flu virus at all. Adults rarely experience any gastrointestinal symptoms of influenza. Children, however, are more susceptible to fluid imbalance—particularly when they have a fever—and may vomit or have diarrhea with the flu and with other flu-like viruses.
