surface of structures…serve as a base upon which the cells might creepHarrison (1914) Viruses exist in a wide spread of varieties with interesting mechanisms for adhering to each other, to neighbouring particles and particularly to living cells which they target by specific means. If this adhesive targeting mechanism changes slightly, then different cells, for example human rather than bird in the case of avian influenza, may be singled out for virus attachment and new infections can result, causing dangerous disease pandemics.Each virus particle, called a virion, may be viewed as a polymer nanoparticle, rather like polystyrene but containing more complex molecules which can assemble and break up depending on the environment. These polymeric virus nanoparticles are normally not very sticky in water and can be observed oscillating in Brownian motion, forming small numbers of doublets and triplets which are a measure of the low adhesion between the virions. This self-adhesion can be varied by altering the chemical conditions of the suspension, for example pH, salt and polymer concentration.Adding polymer molecules to the suspension can increase the adhesion by the depletion effect and crystals of virus particles may solidify out of the liquid. The way in which the free-floating viruses solidify into crystals is another measure of the weak van der Waals bonding between the particles.By adding other particles or cells to the virus suspension, the virus adhesion to other materials process can be investigated to give a precise measure of the adhesion process, especially the adhesion energy and range of attraction. This adhesion depends greatly on the surfactant molecules in solution within the dispersion. The presence of other particles may influence the virus-cell adhesion process and give complex behaviour. More subtle adhesion effects, such as release of budding viruses from infected cell surfaces, have been used to devise new drugs such as Tamiflu, while other phenomena like assembly of virions within cells require further elucidation.