NL Journal of Medical and Pharmaceutical Sciences

Introduction

Influenza A (H3N2) and Dengue fever are two distinct viral illnesses that frequently cause seasonal epidemics in tropical and subtropical regions. Influenza A (H3N2), a subtype of the Orthomyxoviridae family, primarily affects the respiratory tract and is transmitted via aerosolized droplets. It typically presents with fever, sore throat, cough, myalgia, and malaise. In contrast, Dengue fever is a mosquito-borne viral infection caused by the Dengue virus, transmitted by Aedes aegypti mosquitoes. It is characterized by systemic symptoms such as high-grade fever, retro-orbital pain, myalgia, and hematologic abnormalities including thrombocytopenia and elevated hematocrit.

Although both viruses are endemic in many regions, co-infection is rarely reported, particularly in pediatric populations. The overlapping clinical features, fever, headache, myalgia can obscure diagnosis and delay targeted management. In recent years, the simultaneous circulation of respiratory and vector-borne viruses has increased the likelihood of dual infections, especially in densely populated areas with poor vector control and high seasonal transmission. Children, due to their immature immune responses and increased exposure in communal settings, are particularly susceptible.

This case report describes a rare pediatric co-infection of Influenza A (H3N2) and Dengue fever, highlighting the diagnostic challenges and emphasizing the importance of early recognition and supportive care.

Case Report

A 12-year-old girl was admitted with a 4-day history of high-grade intermittent fever (up to 39°C), bifrontal headache, retro-orbital pain, anorexia, and generalized malaise. She also developed dry cough and mucopurulent rhinorrhea over the preceding 2 days, suggestive of an upper respiratory tract infection. There was no history of rash, vomiting, bleeding, abdominal pain, recent travel, or known contact with sick individuals.

On Examination

• General: Febrile (39°C), lassitude, tachycardia (Pulse Rate (PR) 110 beats per minute (bpm), normotensive (Blood Pressure 100/70 mmHg), respiratory rate (RR) within normal limits, no respiratory distress. Anthropometry showed obesity (BMI>27th Adult Equivalent (AE).
• ENT: Swollen nasal turbinates with mucopurulent discharge.
• Systemic: Cardiovascular, respiratory, abdominal, and neurological examinations were unremarkable.

Investigations

Initial laboratory workup revealed:

• Complete Blood Count: Mild leukopenia (4,230 cells/mm³), thrombocytopenia (117,000 cells/mm³), Normal Hemoglobin, normal Hematocrit.
• Liver Function Tests: Mild transaminitis (Aspartate Transaminase (AST): 60 U/L Alanine Transaminase (ALT): 82 U/L).
• Dengue Serology: was sent on 4th day and turned out to be positive for IgM antibodies via ELISA on 6th of illness.
• Respiratory Viral Panel: RT-PCR detected Influenza A and H3N2 RNA.

No evidence of bacterial infection

Management

The patient was admitted for observation and supportive care. Treatment included:

• Hydration: Oral and intravenous fluids to maintain perfusion and prevent hemoconcentration.
• Antipyretics: Paracetamol for fever and discomfort.
• Antiviral Therapy: Oseltamivir 75 mg twice daily for 5days.
• Monitoring: Daily platelet counts, hematocrit levels, and clinical signs of plasma leakage or bleeding.

The fever continued for another 2 days, and she recovered on its own. No antibiotics were administered.

Outcome

The patient showed gradual clinical improvement:

• Fever subsided by Day 6 of illness.
• Upper respiratory symptoms resolved with supportive care.
• No signs of plasma leakage, bleeding, or respiratory distress were observed.
• Platelet count normalized on repeat testing after 48 hours (hrs.) of admission during follow up on 72 in outpatient Department (OPD), and liver enzymes normalized.

She was discharged in stable condition with complete recovery and advised for outpatient follow-up.

Discussion

Co-infection with Dengue virus and Influenza A (H3N2) is a rare but clinically significant occurrence, particularly in pediatric populations. While both viruses are endemic in tropical and subtropical regions, their simultaneous circulation during seasonal peaks increases the likelihood of dual infections [1-3]. The clinical overlap, fever, headache, malaise, and myalgia, can obscure diagnosis, delay appropriate therapy, and potentially lead to adverse outcomes if not promptly recognized [1,4-6].

The diagnostic challenge lies in the shared symptomatology. Dengue fever typically presents with high-grade fever, retro-orbital pain, thrombocytopenia, and systemic manifestations, whereas Influenza A (H3N2) is primarily a respiratory illness characterized by cough, sore throat, nasal congestion, and constitutional symp- toms [2-4]. In this case, the patient exhibited features of both: upper respiratory tract involvement (dry cough, mucopurulent rhinorrhea) and classical dengue indicators (fever, headache, thrombocytopenia), necessitating a broad differential diagnosis.

Laboratory investigations were pivotal in confirming the dual etiology. RT-PCR identified Influenza A (H3N2) RNA, while ELISA detected Dengue-specific IgM antibodies. These findings guided the clinical approach and ruled out other potential causes of febrile illness. In resource-limited settings, where access to multiplex testing may be constrained, such cases risk being misdiagnosed or underreported [3].

The primary concern in co-infections is the potential for compounded complications:

• Dengue Fever: Particularly in its critical phase, may progress to plasma leakage, hemorrhage, or shock [6].
• Influenza A: Especially in children with underlying conditions, can lead to severe pneumonia, secondary bacterial infections, or exacerbation of asthma and other comorbidities [2].

Fortunately, in this case, the patient remained hemodynamically stable and did not exhibit signs of plasma leakage, respiratory distress, or bleeding. The decision to initiate Oseltamivir was based on early detection of Influenza A and the mild clinical course. Supportive care, including hydration, antipyretics, and close monitoring of hematologic parameters, proved sufficient for recovery.

Although most pediatric co-infections are self-limiting, the potential for synergistic viral interactions and immune dysregulation warrants careful observation. This case reinforces the importance of maintaining a high index of suspicion for co-infections during overlapping outbreak seasons and highlights the value of early diagnostic testing in guiding management [1-6].

Conclusion

This case underscores the importance of considering viral co-infections in pediatric patients presenting with febrile illness, particularly in endemic regions during overlapping outbreak seasons. Early diagnostic workup and supportive management are pivotal in ensuring favorable outcomes. Clinicians should maintain a high index of suspicion and utilize multiplex testing strategies to differentiate and identify concurrent infections.

Limitations

• Dengue Serotyping: Could have provided further insight into the clinical severity and epidemiological relevance of the infection.

References

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