What is the approximate duration of viraemia in dengue infection, during which the virus is detectable in blood and mosquitoes can acquire infection?

Explanation

## Viraemia Period in Dengue **Key Point:** The viraemia phase in dengue typically lasts 3–5 days (range 2–7 days), during which the virus circulates in the blood and is transmissible to mosquitoes. ### Timeline of Dengue Infection ```mermaid flowchart TD A[Mosquito bite<br/>Virus inoculation]:::outcome --> B[Incubation period<br/>3-14 days<br/>avg 5-6 days]:::outcome B --> C[Onset of symptoms<br/>Fever, headache, myalgia]:::outcome C --> D[Viraemia phase<br/>3-5 days<br/>Virus detectable in blood]:::action D --> E[Defervescence<br/>Fever subsides]:::outcome E --> F[Post-febrile phase<br/>Convalescence<br/>Antibodies appear]:::outcome F --> G[Lifelong immunity<br/>to that serotype]:::outcome ``` ### Clinical Correlation with Viraemia | Phase | Duration | Clinical Features | Viral Detection | |-------|----------|------------------|------------------| | **Incubation** | 3–14 days | Asymptomatic | Virus in blood (late phase) | | **Febrile/Viraemic** | 3–5 days | High fever, myalgia, headache, rash | **Peak viraemia** | | **Critical phase** | 1–2 days | Defervescence, plasma leakage risk | Viraemia declining | | **Recovery** | 7–10 days | Convalescence | Antibodies present, virus absent | **High-Yield:** Viraemia is highest during the first 2–3 days of fever; this is the window for mosquito-to-human transmission. After defervescence, viraemia rapidly declines and transmission risk falls sharply. **Clinical Pearl:** Patients are most infectious to mosquitoes during the febrile phase (when they seek medical care). Isolation or mosquito protection during this period is critical for outbreak control. **Warning:** ~~Viraemia persists for 2–3 weeks~~ — this is incorrect. Viraemia is brief (3–5 days); prolonged viraemia is rare and suggests secondary dengue or dengue haemorrhagic fever.