Dengue vs. Flu: How Do You Know the Difference?

Because catching it early could save your life. 

In the Philippines, the rainy season doesn’t just bring thunderstorms—it also brings a spike in illnesses. While the flu is common this time of year, there’s another threat you shouldn’t ignore: dengue fever. The tricky part? Both illnesses can start with the same signs: fever, fatigue, and body aches. 

So how do you know if it’s just the flu or something more serious? 

Let’s do a deep dive. 

It Starts With a Fever—But What Comes Next Matters 

Flu usually comes with the “classic” cold symptoms—sore throat, cough, runny nose, and a general sense of tiredness. You might feel weak, have a low to moderate fever, and want to stay in bed for a day or two. But Dengue feels more intense. 

People with dengue often experience a sudden spike in temperature—up to 40°C—and it doesn’t go away easily. There’s often a pounding headache, usually behind the eyes, and a heavy, deep pain in the joints and muscles (that’s why dengue’s nickname is “breakbone fever”). As the days go on, you might even notice skin rashes, nausea, or minor bleeding like bleeding gums or a nosebleed. Additionally, dengue pathognomonic rash appears 2-5 days from the onset of fever, hemoconcentration CBC and decreasing trend in platelet due to hemolysis. 

Meanwhile, a person with the flu will usually get better on their own in a few days. But dengue can worsen quickly, especially without medical attention. There lies the danger. 

Flu Spreads Fast—But Dengue Bites Hard 

Here’s another key difference: flu is contagious, and spreads when someone sneezes or coughs near you. Dengue doesn’t spread person-to-person—it’s passed through the bite of the Aedes mosquito, the small striped ones that breed in stagnant water. 

That means if someone in your area has dengue, and there are mosquitoes around? You could be next. 

Know When to See a Doctor 

If your fever lasts more than two days, or if you start to feel unusually weak, have stomach pain, or notice bleeding or bruising—you need to get checked right away. Dengue can progress into severe forms like Dengue Hemorrhagic Fever or Dengue Shock Syndrome, both of which can be fatal if ignored. 

The flu rarely causes these kinds of complications—but it can still be dangerous for young kids, the elderly, or those with weak immune systems. So whether it’s dengue or the flu, listen to your body. If something feels off, don’t brush it off. 

Better to Be Sure

With so much overlap in early symptoms, it’s understandable to feel confused. The best thing you can do is not guess—get HealthFirst Clinic’s dengue testing. A quick visit to your doctor or clinic can make all the difference in starting the right treatment early. 

👨‍⚕️ Need clarity fast? 

At HealthFirst Clinic, we offer fast and accurate dengue and flu diagnostics like Dengue Blot Test, CBC with platelet, plus expert care from doctors who listen. 

  👉 Schedule your check-up today at info@healthfirst.com.ph or call us at (02) 8860 9740.  

Sources: 

• World Health Organization – Dengue and Severe Dengue 

• Centers for Disease Control and Prevention – Influenza Symptoms 

• Philippine Department of Health – Dengue Updates