Respiratory Syncytial Virus (RSV) is a clinically important virus and is the leading viral cause of lower respiratory tract infection in infants and also causes severe infections in the elderly. RSV infects approximately 60 million people and is responsible for an estimated 160,000 deaths annually worldwide.

Scanning Electron Microscopy (SEM) allows scientists to look at virus infected cells at very high magnification. This image shows filamentous virus particles emerging (budding) from an infected cell. To identify the virus, viral proteins are labelled with small gold beads. These can be detected in the SEM and are shown here in red.

Fluorescently labelling parts of a virus or cell allows researchers to look at them with a high-resolution 'confocal' microscope. This microscope uses lasers to illuminate the fluorescent markers and can be used to view the cell in 3D. This is a powerful way of examining how viruses behave in infected cells.