Viruses are the least treatable and most common cause of infectious disease in humans. Viral illnesses range from minor – the common cold, herpes simplex cold sores – through to life threatening such as HIV, fulminant hepatitis, haemorrhagic illness such as Ebola, and various virally induced cancers. Viruses are very simple microorganisms that are unable to replicate outside their host cells. The clinical manifestations of viral illnesses arise due both to direct effects of the virus on host tissues and to immune responses. 

Many new viral diseases have emerged in the last 60 years – for example HIV and SARS - and the ability of viruses to rapidly undergo mutations means that host immunity is constantly challenged. Evidence of the adaptability of viruses is found in the family of influenza viruses that manage to sufficiently alter their genetic material to reinfect entire populations on a seasonal basis. Antiviral drug therapy has advanced considerably in the last three decades but many types of virus remain invulnerable to therapy. For these pathogens, the main protection is immunisation.

The occurrence or threat of pandemics in the last ten years has created much media interest, including the making of films such as Contagion.the appearance of several highly virulent strains of influenza in recent years, and the Middle East respiratory syndrome (MERS) has generated considerable discussion about the transmission of viruses from animal to human hosts and how these viruses are then able to transmit from human to human – a key step in the evolution of a pandemic. Nurses need to have an understanding of viral illnesses to support both public health policies and individual clients with viral diseases.

After completing this online learning activity and quiz you should be able to:

• Describe the structure and replication of viruses
• Outline the common types of viruses that cause disease in humans and the mechanisms contributing to their pathogenicity.
• Describe the actions of classes of antiviral drugs.
• Discuss factors that contribute to transmission of viral illnesses and the development of epidemic or pandemic disease.

The PDF attached to this activity first appeared in the May 2013 issue of Kai Tiaki Nursing New Zealand. The activity has been updated since this time and the content is not identical.