According to "Harrison's Principles of Internal Medicine," acute respiratory illnesses such as colds and flu account for 30 to 50 percent of time lost from work and 60 to 80 percent of time lost from school each year. Colds and flu share many of the same symptoms, which can make it difficult to tell the difference. However, there are a few ways you can distinguish between the two.
Onset
According to the American Academy of Family Physicians (AAFP), the symptoms of a cold develop slowly while the symptoms of flu usually start suddenly. In fact, notes Dr. Raphael Dolin in "Harrison's Principles of Internal Medicine," it's not uncommon for patients with flu to recall the precise time they became ill. By contrast, patients with a cold often predict that they are getting sick a few days before full-blown symptoms appear.
Symptoms
Although colds and the flu share many of the same symptoms such as fever, fatigue and headache or muscle pain, according to the AAFP, there are some differences. Sneezing and watery eyes are more common with a cold while nausea, poor appetite and chills usually point to flu. In addition, notes a 2009 report in the "Journal of Clinical Microbiology and Infections," with flu, upper respiratory symptoms such as stuffy or runny nose and sore throat tend to develop a few days after cough and other symptoms are already established and the cough associated with flu is usually dry or "non-productive," unlike the mucousy, congested cough associated with a cold.
Severity
Both colds and flu follow a spectrum of severity. While both may be associated with fever, according to the AAFP, a fever under 102 degrees F is more likely to be a cold while a fever over 102 degrees F is more likely to be the flu. In addition, while both colds and flu can make breathing uncomfortable or more of an effort than normal, colds rarely result in impaired oxygenation. According to the 2009 report in the "Journal of Clinical Microbiology and Infections," 22 percent of people with flu reported shortness of breath or other breathing problems and pneumonia, although rarely seen with colds, according to "Harrison's Principles of Internal Medicine," is the most common complication of the flu.
References
- Influenza (Chapter): R. Dolin; In: "Harrison's Principles of Internal Medicine, 17th edition;" A.S. Fauci, E. Braunwald, D.L. Kasper, S.L. Hauser, D.L. Longer, J.L. Jameson and J. Loscalzo (Eds.); 2008
- American Academy of Family Physicians: Colds and the Flu
- "Clinical Microbiology and Infections;" Dynamics of Clinical Symptoms in a Case with Pandemic Influenza A (H1N1); CS Lee and JH Lee; Nov. 13 2009
