COVID, flu or RSV? How to tell the three common diseases apart

Science and Health

The coronavirus is making a big comeback, and if that wasn’t enough, there are more and more cases of the flu and RSV.

According to the Health Ministry data, since the start of October 2022 until the end of December, there were 1,843 people hospitalized with the flu, of which 356 were hospitalized in the last week.

The flu can cause serious illnesses like pneumonia, as well as other respiratory complications, heart muscle inflammation and even death. The only real way to protect yourself from the flu is the flu vaccine.

And according to the Health Ministry data, in the same period of time, 1,808 people were hospitalized with RSV (respiratory syncytial virus) – a common cause of respiratory diseases. Four hundred and nine of them were hospitalized in just the last week of the year.

RSV causes respiratory diseases, especially in babies and toddlers under the age of two, where it manifests as bronchiolitis.

And in addition to all of this, there are more and more patients with COVID. In the last week of 2022, there were over 1,000 new cases per day on average with no signs of stopping. At the start of 2023, there were 12,315 coronavirus patients in Israel, 545 of them hospitalized.

The novel coronavirus (top) and influenza (bottom) viruses are seen in this composite image. (credit: Wikimedia Commons)

How do you differentiate between the three sicknesses?

One of the main problems is that it is difficult to distinguish between these diseases. Lots of people suffer from breathing difficulties, coughs, sore throat and fevers – and these could be symptoms of all three of these viruses. So how do you know when to do a COVID test?

Although there are quite a few similar symptoms, each disease also has some unique ones, as well as differing in how the diseases progress. Here are five characteristics you can use to differentiate between COVID, RSV and the flu:

  1. Typical symptoms: Loss of smell and taste are more common in COVID compared to RSV and the flu. Likewise, wheezing is more common in severe RSV.
  2. Speed of the onset of symptoms: Flu symptoms tend to appear much more suddenly than RSV or COVID, so there will usually be a rapid and sudden onset of high fever. With the other two, the symptoms tend to come on more gradually and slowly worsen.
  3. Incubation time: Each of the three viruses has different incubation periods. As such, it’s important to understand when the exposure to each of them was. Flu symptoms tend to manifest around two days after exposure; COVID manifests around three to four days after; and RSV appears around four to six days after exposure.
  4. Patient age: Age plays a very important role in the severity of symptoms. An otherwise healthy adult is unlikely to suffer severe RSV symptoms, compared to the flu or COVID. People who suffer from severe RSV will be babies, children with preexisting lung conditions, elderly adults or immunocompromised patients.
  5. The neighborhood virus: This is another hint at what you’re sick with. All three viruses are highly contagious and there’s a good chance communities will all get infected with the same disease. Were you just at a birthday party in a closed space and everyone tested positive for COVID-19? Chances are, if you start developing symptoms, you’ll test positive for COVID too.