For how long can the Widal test remain positive after a typhoid infection?

Duration of Widal Test Positivity After Typhoid Infection

The Widal test typically remains positive for 2-7 months after typhoid infection, with IgM antibodies persisting for approximately 2.6 months and IgG antibodies for approximately 5.4 months. 1

Antibody Persistence Timeline

IgM Antibodies

• Mean persistence: 2.6 months (95% CI: 2.0-3.1 months) after documented typhoid fever 1
• Positive IgM results within 4 months of previous typhoid infection should be interpreted with extreme caution in endemic areas 1

IgG Antibodies

• Mean persistence: 5.4 months (95% CI: 4.5-6.3 months) after documented typhoid fever 1
• Positive IgG results within 7 months of previous typhoid infection should be interpreted cautiously in endemic areas 1

Critical Clinical Implications

Interpretation Pitfalls

• A positive Widal test does NOT necessarily indicate acute infection if the patient had typhoid within the past 7 months 1
• In endemic areas where typhoid is common, background antibody titers can persist from previous infections, creating a "hyperimmune state" that complicates interpretation 2
• The test can remain positive even after successful treatment and clinical recovery 1

When Widal Results Are Misleading

• False positives occur in 11.5% of patients with major immunological disturbances, requiring cautious interpretation in these populations 2
• Patients from endemic areas may have persistently elevated titers from past exposures, making single-point testing unreliable 1
• The presence of antibodies months after infection explains why the Widal test should never be used alone for diagnosis 1

Diagnostic Recommendations

Optimal Testing Strategy

• Blood culture remains the gold standard and should always be obtained before relying on Widal testing 3, 4
• If Widal testing is used, paired acute and convalescent sera (7-10 days apart) provide superior diagnostic accuracy compared to single testing 5
• Convalescent-phase testing achieves 90% sensitivity and specificity with O antigen titers ≥1:200, compared to only 52% sensitivity with acute-phase testing alone 5

Practical Guidance

• Do not use Widal test results to guide treatment decisions if obtained within 7 months of known or suspected previous typhoid infection 1
• In endemic areas, interpret any positive Widal result in the context of the patient's exposure history and timing of previous infections 1
• For patients requiring proof of cure or clearance (e.g., food handlers), repeat blood cultures are required rather than Widal testing, as antibodies persist long after viable organisms are eliminated 6