Q: My baby has had a high fever up to 40°C for 5 days with no cold symptoms. Could it be Roseola?
- Myeongchan Kim, MD
- Jun 27
- 3 min read
Updated: Jul 8
Medically reviewed by Sang Hyun Ahn, MD
Content edited by Myeongchan Kim, MD
This post is a dramatization of a question and answer session experienced by our actual medical reviewers. Please note that this content is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
Question:
My baby developed a fever of 38.4°C on the evening of Day 1. I took them to the clinic the next day, and the doctor said the fever was likely due to a swollen throat. I was told to return for a flu test if the fever reached 40°C and the baby became lethargic. On Days 3 and 4, the fever spiked to 39°C, but the baby wasn't lethargic, so I continued the prescribed medication. However, the fever didn't seem to break.
On the dawn of Day 5, the fever hit 40°C, so I gave additional fever reducers. By the morning of Day 5, the baby's condition was good, and the fever seemed to drop, but it went back up to 39°C in the afternoon. There are absolutely no cold symptoms, and a fever rash hasn't appeared yet. Could this simply be roseola (sudden rash)?
Answer:
It is completely understandable that you are very worried, especially since your baby's fever has persisted for five days and even reached 40°C.
Based on your description, here is an evaluation of the current situation:
• High fever of 38.4°C to 40°C persisting for 5 days.
• No other cold symptoms apart from a swollen throat.
• The baby's overall condition and energy levels are relatively good.
• No fever rash has appeared yet.
This pattern certainly suggests the possibility of Roseola (exanthema subitum). Roseola is very common in children between 6 months and 2 years old, and it is typically characterized by 3 to 5 days of high fever without significant cold symptoms, followed by a sudden skin rash right as the fever breaks.
However, a high fever lasting for 5 days requires prompt clinical re-evaluation. Please visit your pediatrician or a medical clinic immediately.
A follow-up visit is necessary right away because:
• The high fever has lasted for 5 days.
• The temperature reached 40°C.
• The exact cause of the prolonged fever is still unclear.
Your baby will likely need the following tests today to ensure an accurate diagnosis:
• Blood test (to check for bacterial infections)
• Urine test (to rule out a urinary tract infection, which often presents as a fever with no cold symptoms)
• Flu or COVID-19 testing
In the meantime, continue the following care at home:
• Cross-administer different classes of fever reducers (e.g., ibuprofen and acetaminophen) at 4-6 hour intervals if the fever remains dangerously high.
• Ensure frequent fluid intake to keep the baby well-hydrated.
• Dress the baby in light, breathable clothing.
⚠️ Go to the Emergency Room immediately if your baby experiences any of the following:
• Seizures or convulsions
• Decreased consciousness or extreme lethargy
• Difficulty breathing
• No urination for more than 8 hours
While this could be a simple viral infection like roseola, a high fever lasting 5 days could indicate a bacterial infection or something more complex. An in-person medical evaluation is essential to confirm the diagnosis and ensure your baby gets the correct care.
For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.
