Electron microscope appearance of Hantaan virus, the causative agent of Korean haemorrhagic fever.

The morphology and morphogenesis of three strains of Hantaan virus, which causes Korean haemorrhagic fever (KHF), were examined by thin-section and negative-contrast electron microscopy of infected A549 cell-culture specimens. In thin sections, virus was detected within cytoplasmic granular matrices (viroplasms) of the infected cells. Virus particles were spherical (diameter 73 +/- 5 nm), and had an extremely electron-dense core (diameter 47 +/- 6.5 nm). Replication and maturation of the virus seemed to occur in the viroplasm. As infection progressed, viral particles increased in number and were packed into the granular matrices as cytoplasmic crystalline arrays. Viruses seemed to be released from infected cells by cell dissolution. Negative-contrast staining showed that the virus had an icosahedral structure (diameter 80 +/- 2 nm) and annular surface capsomeres. Viruses clumped when exposed to anti-Hantaan virus serum from a convalescent patient. The morphology and morphogenesis of the virus were compatible with those of orbiviruses.