As the latest updates indicate, flu activity is increasing across the United States. Currently, it is said to be "widespread" in 24 states, according to the Centers for Disease Control and Prevention. 

But when falling sick with symptoms like coughing, headaches, and tiredness, it can be easy to confuse the flu with a cold. While one should definitely see a doctor to receive a diagnosis during this high-risk period, here are some of the main differences between the two you should know about.

1. Onset of symptoms

When you have a cold, the onset of symptoms tends to be gradual. Signs like a runny nose or a bad cough may take a couple of days to develop and will last for around a week. However, symptoms of the flu are relatively abrupt and a lot more severe.

"With influenza, it hits you very hard, very suddenly," said Dr. Alan Taege, an infectious disease specialist at Cleveland Clinic. "You feel like all of a sudden something happened today. You feel achy, you're tired, and your symptoms are more severe."

2. Presence of fever

Your temperature could help indicate which of the two you are likely suffering from. Usually, a cold is not accompanied by fever — if it is, the fever will be mild at most.

But if your fever occurs suddenly and is in the range of 100 to 102 degrees Fahrenheit, chances are you have the flu. Sometimes, particularly in the case of children, the temperature could even exceed this range.

3. Season

Though you are likely to develop a cold during the winter season, it is possible to catch one even during the summer, spring, or fall seasons. But as we all know, there is a "flu season," one that the U.S. is currently in the middle of. Starting in November and ending in March, symptoms during this time may indicate something worse than a cold.

Nevertheless, timing can only serve as a clue and not a confirmation. "Unfortunately, the flu and a cold cannot be reliably told apart by either the symptoms or the time of year," stated PharmacyTimes.

4. Aches and weakness

The pain and discomfort associated with a cold are quite tolerable with symptoms involving a hacking cough at worst. But, as WebMD notes, the flu can be much worse as it is common to experience chest discomfort and increasing severity in symptoms.

But those will the flu can experience a severe ache in their muscles all over their body. Though one could feel a bit weak while having a cold, flu symptoms are more along the lines of extreme exhaustion, especially when the illness is in the initial stages.