Understanding machupo virus: A neglected arenavirus with global health importance

Table 3 Diagnostic methods

Diagnostic method	Principle	Specimen	Optimal timing	Advantages	Limitations
RT-PCR	Detects viral RNA by reverse transcription followed by amplification	Whole blood, serum, plasma	Early acute phase (first 1-10 days of illness)	High sensitivity and specificity; rapid; confirms active infection	Requires specialized laboratory (BSL-4 for handling live virus); expensive; limited availability in endemic regions
Real-time RT-PCR (qRT-PCR)	Quantifies viral RNA in real time using fluorescent probes	Whole blood, serum	Early acute phase	Fast; quantitative; highly sensitive; useful for monitoring viral load	Same biosafety and infrastructure requirements; costly
Virus isolation (cell culture)	Growth of live virus in susceptible cell lines	Blood (acute phase)	Early acute phase	Definitive diagnosis; allows further characterization	Requires BSL-4 containment; slow; high biohazard risk
Antigen detection (ELISA)	Detects viral proteins using specific antibodies	Serum, plasma	Acute phase	Faster than culture; useful when PCR unavailable	Lower sensitivity than PCR; cross-reactivity possible
IgM ELISA	Detects virus-specific IgM antibodies	Serum	Late acute to early convalescent phase (after about 5-7 days)	Indicates recent infection; safer than virus isolation	Not useful in very early phase; possible cross-reactivity with other arenaviruses
IgG ELISA	Detects virus-specific IgG antibodies	Serum	Convalescent phase	Indicates past exposure or recovery	Cannot confirm acute infection alone
Immunohistochemistry	Detects viral antigens in tissue using labeled antibodies	Tissue samples (biopsy or autopsy)	Severe/fatal cases	Useful in post-mortem diagnosis	Invasive; requires specialized labs
Next-generation sequencing	Detects and sequences viral genome directly from specimen	Blood, tissue	Acute phase	Comprehensive; detects variants; useful for outbreak investigation	Expensive; limited access; requires advanced bioinformatics

PCR: Polymerase chain reaction; RT-PCR: Reverse transcription polymerase chain reaction; ELISA: Enzyme-linked immunosorbent assay; BSL: Biosafety level.