| Dengue virus | Flavivirus | 3–10 | Usually none; 70% asymptomatic | Erythema early on (“islands of white in a sea of red”), maculopapular or urticarial exanthem in febrile phase (50%–80%) | Leukopenia, thrombocytopenia, elevated transaminases Dengue PCR or NS1 Ag positive in first 7 days of illness; dengue IgM positive after 5 days of illness in 80% | Second infections carry 5% risk of hospitalization and severe dengue (hemorrhagic or third spacing); infants at high risk of severe dengue because of maternal antibodies |
| Zika virus | Flavivirus | 3–7 | Variable; 80% asymptomatic | Common (70%–85%); erythema, macular, or maculopapular and very pruritic | Leukocytosis, thrombocytopenia, elevated transaminases Zika blood PCR diagnostic in first 5–10 days; Zika IgM positive in 5–15 days; false-positives occur in dengue endemic areas | Nonpurulent conjunctivitis (60%), facial and neck edema (70%) |
| Yellow Fever virus | Flavivirus | 3–6 | Fever, muscle pain, backache, headache, shivers, vomiting in acute phase | Acute phase: facial flushing, conjunctival hyperemia Toxic phase (15%): jaundice, petechiae, hemorrhage | Leukopenia, thrombocytopenia, elevated transaminases and bilirubin; blood PCR positive in first 5–7 days, IgM positive in 5–15 days | 40%–50% mortality rate in those progressing to “toxic” stage Vaccine confers lifelong immunity |
| West Nile virus | Flavivirus | 3–14 (≤28) | 70% symptomatic; high fever (>39°C), headache, severe polyarthralgia, myalgia | Affects ~20%; small pink to red macules and papules on the torso and proximal extremities | Mild leukocytosis and hyponatremia PCR positive in first 3–5 days of illness but usually negative when presenting IgM and IgG serology most helpful | Hospitalization in 30%; fatigue for 1 mo in 95%; neuroinvasive disease in 1% |
| Chikungunya virus | Alphavirus | 2–6 | Fever, headache, flulike symptoms, myalgia, GI symptoms | Variable: morbilliform, vesiculobullous, and psoriatic-like presentations; postinflammatory hyperpigmentation | Leucopenia and lymphopenia PCR positive first in 3 days of illness IgM and IgG serology after 1 week of illness | Symmetric arthralgia and arthritis in 70% (can last 6–12 mo) |
| Mayaro virus | Alphavirus | Unknown | Acute febrile illness with headache, malaise; red eyes in 45% | Rash with pruritus in 30%–50% | Leucopenia IgM and IgG ELISA | Endemic in South America and the Caribbean Arthralgia and arthritis in 50%–90% (can last 6–12 months) |
| O’nyong-nyong virus | Alphavirus | Unknown | Acute febrile illness in 80%–100%, headache, myalgia | Rash in 70%–90% | Leucopenia IgM and IgG ELISA | Outbreaks in Africa Arthralgia and arthritis in 60%–100% (can last 6–12 mo) |
| Ross River virus | Alphavirus | 7–9 | Acute febrile illness in 20%–60%, headache, photophobia | Rash in 40%–50% | Leucopenia IgM and IgG ELISA | Endemic ... |