The WHO declared smallpox eradicated in 1980. However, concern over its potential use by terrorists or in biowarfare has led to striking growth in research related to this much-feared disease. Modern molecular techniques and new animal models are advancing our understanding of smallpox and its interaction with the host immune system. Rapid progress is likewise being made in smallpox laboratory diagnostics, smallpox vaccines, and antiviral medications. WHO and several nations are developing stockpiles of smallpox vaccine for use in the event the disease is reintroduced. National and international public-health agencies have also drawn up plans to help with early detection of and response to a smallpox outbreak. These plans hinge on physicians' ability to recognise the clinical features of smallpox and to distinguish it from other illnesses characterised by rashes.