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This story originally appeared on Business Insider
It is COVID-19 or just one flu?
This is a question many people are likely to ask themselves in the fall and winter as coronavirus infections overlap with cases of the common cold and seasonal flu. Symptoms can be difficult to tell apart as all three conditions can cause a cough.
However, there are peculiarities of every disease.
A recent study by the University of Southern California identified a different order of symptoms in COVID-19 patients: most symptomatic patients begin with a fever followed by a cough. With seasonal flu, the opposite is often the case: people usually develop a cough before they have a fever.
If you have a cold, the Centers for Disease Control and Prevention says the more likely you will start with a sore throat as the first symptom.
How to distinguish the new coronavirus from seasonal flu, allergies, and colds.
Image: Yuqing Liu | Insider via Business Insider / Translation: in Spanish
However, these lists of symptoms for each illness and the order in which they appear are not infallible: some COVID-19 patients do not develop a fever, and some flu patients never get a cough.
It is therefore also helpful to consider how quickly symptoms appear and how long they last.
How COVID-19, flu, cold and allergies manifest and progress
Coronavirus cases tend to develop gradually compared to the flu. While some people develop symptoms of COVID-19 within two days of being infected, it can take up to two weeks for symptoms of the disease to manifest. On average, people feel sick five days after being infected.
By contrast, people with the flu usually feel sick within one to four days of exposure. Most patients recover completely in less than two weeks, often in as little as a few days.
Some coronavirus patients can also recover within two weeks, but an increasing proportion of patients have reported symptoms that last for several months.
In contrast, cold symptoms usually appear within two to three days of infection, but like the coronavirus, they often develop gradually. And some symptoms last longer than others: people with a typical cold may have a sore throat for eight days, a headache for nine to ten days, and a constipation, runny nose, or cough for more than two weeks.
Allergies usually last longer (around two to three weeks per allergen) and only subside when the allergen is released from the air. Seasonal allergies also tend to be more severe in the spring.
The most common symptoms of any disease
Coronavirus cases range from asymptomatic to mild and severe.
“I’ve never seen an infection with this variety of manifestations,” Anthony Fauci, director of the National Institute for Allergies and Infectious Diseases, told Facebook founder Mark Zuckerberg in July.
Some patients have even reported conditions that are not on the official CDC list, such as hair loss, hiccups, and swollen and purple toes.
Coronavirus testing in Jericho, New York, April 22, 2020 / Image: J. Conrad Williams, Jr. | Newsday RM | Getty Images via Business Insider
Many COVID-19 patients lose their sense of taste or smell, which is possibly the strongest predictor of COVID-19 infection, according to a June study by scientists at Massachusetts General Hospital and King’s College London. A Spanish case study found that almost 40% of COVID-19 patients developed odor and / or taste disorders compared to just 12% of flu patients.
Symptoms like fever or headache can also help rule out allergies or colds.
In the meantime, people with colds are more likely to have runny or stuffy noses than COVID-19 patients. And cold symptoms are generally milder.
But one of the hallmarks of allergies, itchy eyes, is not associated with any of the other three diseases.
Ultimately, the best way to tell if you have COVID-19 is through a diagnostic test. People who haven’t been tested should stay home if they feel sick or have been exposed to someone with the virus.
Everyone should get a flu shot this fall to minimize the possibility of overcrowding in hospitals while treating flu and COVID-19 patients.
“In my opinion this will be the most important flu season of our lives,” said US Surgeon General Jerome Adams on Wednesday at a Senate hearing.
“Less flu and fewer hospital stays help save valuable health care resources.”