Hantavirus Laboratory Diagnosis — PCR, Serology, Antigen Capture and What Each Test Actually Tells You

How does a clinical microbiology lab actually confirm hantavirus? The answer matters operationally — a misdirected test or a misinterpreted negative result can delay ICU admission in a disease where hours determine survival. This article walks through each lab method in current use, when it is the right test, and what its limitations are. It is written for clinicians, public-health investigators and informed patients, but the intuition is accessible.

RT-PCR (reverse-transcription PCR)

RT-PCR is the central acute-diagnosis test for hantavirus. It detects viral RNA directly in patient samples — typically EDTA whole blood or plasma in the first week of illness, sometimes respiratory specimens or autopsy tissue.

• Window: Best in the first 5-7 days of symptoms, when viraemia is highest. Sensitivity drops rapidly after day 7 as the immune response clears virus from blood.
• Time to result: 90 minutes (Cepheid GeneXpert assay) to 4 hours (in-house RT-PCR) at most reference labs.
• Sensitivity:>90% in the optimal early window for symptomatic patients.
• False negatives: Possible in the first 24 hours of symptoms as viraemia is still ramping up. Repeat testing in 24-48 hours is standard for high-suspicion patients.
• Strain specificity: Modern multiplex panels differentiate ANDV from Sin Nombre, Puumala, Hantaan and related strains in a single run. Important for international investigations like MV Hondius.

IgM and IgG serology

Serology detects the host antibody response to infection rather than the virus itself. Two antibody classes matter:

• IgM: Appears within 5-7 days of symptom onset. Indicates current or recent infection. Most useful for confirming a clinical case where PCR may already be falling negative.
• IgG: Appears within 1-3 weeks of onset, persists for years. Indicates current or past infection. Used for epidemiological surveys and to confirm seroconversion.

Paired acute and convalescent serology — one sample on presentation, a second 2-4 weeks later — is the gold standard for retrospective confirmation. Useful when PCR was missed or negative.

Antigen-capture immunoassays

Antigen-capture tests detect viral nucleocapsid protein in patient samples directly. They are faster and less infrastructure-heavy than PCR — useful in field-deployable testing in resource-limited endemic regions like rural Argentine Patagonia.

Sensitivity is generally lower than PCR (around 70-80%), so a positive result is informative but a negative does not rule out infection in the setting of strong clinical suspicion.

Next-generation sequencing (NGS)

Whole-genome sequencing of hantavirus isolates is increasingly deployed in outbreak investigations. For the MV Hondius cluster, sequencing the index isolates and comparing them with reference strains from Patagonia is how investigators are mapping the outbreak's geographical origin and ruling in or out person-to-person transmission chains.

• Time to result: 2-5 days at well-equipped reference centres.
• Sample requirements: Sufficient viral RNA from PCR-positive samples; usually requires the original blood sample.
• Cost: Higher than PCR, but increasingly accessible.
• Public-health value: Phylogenetic analysis informs whether two cases share a common source. WHO uses NGS data to publish reference sequences for laboratory comparison worldwide.

Virus isolation

Cell-culture isolation of hantavirus is technically demanding and requires BSL-3 containment. It is rarely done for clinical diagnosis but remains important for research, vaccine development and reference-strain characterisation. Most clinical microbiology labs do not isolate; they refer suspect samples to national reference centres.

What test should you ask for?

For a symptomatic patient with possible exposure:

1. RT-PCR on EDTA blood — first and most important.
2. IgM serology in parallel — the result will lag PCR by a day or two but is informative.
3. Convalescent IgG serology at 2-4 weeks — completes the retrospective picture.
4. Repeat PCR at 24-48 hours if first test is negative and clinical suspicion remains high.
5. For research or detailed outbreak investigation, request isolate referral to a national reference centre for sequencing.

Related reading

• Hantavirus clinical diagnosis — when to suspect
• 12 questions to ask your doctor about testing
• Tristan da Cunha airdrop — portable PCR in the field