Viral Infections Causing Intermittent Fevers, Headache, and Body Aches Lasting Up to Two Weeks
Influenza is the most likely viral infection causing intermittent fevers, headache, and body aches lasting up to two weeks, as uncomplicated influenza illness typically resolves after 3-7 days but cough and malaise commonly persist for more than 2 weeks. 1, 2
Primary Consideration: Influenza
Influenza presents with the exact symptom constellation described and has a characteristic biphasic pattern that can create the appearance of intermittent symptoms:
- Influenza characteristically presents with abrupt onset of fever, myalgia (body aches), headache, severe malaise, nonproductive cough, sore throat, and rhinitis 1, 3
- Uncomplicated influenza illness typically resolves after 3-7 days for the majority of persons 1, 2
- Critically, cough and malaise can persist for more than 2 weeks even after other symptoms resolve, which explains the extended duration 1, 2
- Fever in influenza tends to occur early in the illness, often in concert with constitutional symptoms such as headache and myalgias, typically disappearing in the first 24-48 hours while respiratory symptoms become more prominent 1
Key Distinguishing Features of Influenza
- The incubation period ranges from 1-4 days, with an average of 2 days 2, 3
- Adults are infectious from the day before symptom onset through approximately 5-6 days after illness begins 2
- Mild illness without fever can occur and has been reported in 6-33% of persons infected 1
- Young children may present atypically with otitis media, nausea, and vomiting 1, 2
Alternative Viral Considerations
While influenza is most likely, other viral infections can present similarly but are less common:
Dengue Fever
- Dengue presents with fever, headache, retro-orbital pain, myalgia, arthralgia (particularly back pain), and rash 1
- The incubation period is 4-8 days (range: 3-14 days) 1
- However, dengue typically does not cause the intermittent fever pattern described and is geographically restricted to tropical regions, particularly Asia and South America 1
Chikungunya
- Chikungunya presents with fever and prominent polyarthralgia or arthritis 1
- The incubation period is 2-3 days (range: 1-12 days) 1
- This infection is less likely given the emphasis on body aches rather than joint-specific pain 1
Critical Pitfalls to Avoid
Do not assume the diagnosis based on symptoms alone:
- Respiratory illnesses caused by influenza are difficult to distinguish from other respiratory pathogens based on symptoms alone, with clinical definitions showing sensitivity of only 63-78% and specificity of 55-71% compared to viral culture 2
- Other respiratory pathogens that may present with similar illness include respiratory syncytial virus (RSV), adenovirus, rhinovirus, parainfluenza virus, as well as bacterial pathogens such as Chlamydia pneumoniae, Legionella sp, Mycoplasma pneumoniae, and Streptococcus pneumoniae 1
The predictive value of clinical diagnosis increases significantly when influenza is known to be circulating in the community 1
When to Consider More Serious Diagnoses
Seek immediate evaluation if any of the following are present:
- High fever (≥39°C) with purulent nasal discharge present concurrently for the first 3-4 days suggests severe bacterial sinusitis rather than simple viral infection 1
- Symptoms persisting beyond 10 days without improvement warrant consideration of acute bacterial sinusitis 1
- Recent freshwater exposure (swimming in lakes/rivers) within 2-30 days before symptom onset, particularly with severe calf pain and conjunctival suffusion, suggests leptospirosis rather than typical viral infection 4
- Neuropsychiatric symptoms, profound disorientation, or seizures warrant consideration of viral encephalitis 1
Treatment Implications
For suspected influenza: