The Contributions of Virus Infections to our Understanding of the Immune System
Viruses, on the one hand, symbolise mankind’s greatest achievements in controlling infectious diseases yet on the other hand, they still constitute a very great public health risk and provide a scientific challenge to make effective, safe and inexpensive vaccines. Vaccines against smallpox, yellow fever, polyomyelitis, measles and rubella have been or are very successful. Smallpox has been eradicated and transmission of measles reduced to extremely low levels in the USA following the need for parents to provide evidence of vaccination prior to admittance of their children to school. Immunisation with current vaccines to control measles and poliomyelitis is sufficiently effective to suggest that in principle measles could be eradicated and there is a plan to eradicate poliomyelitis in the Americas. In contrast, there are other viral infections of global importance for which either current vaccines are inadequate or too costly or vaccines are unavailable. These include the following viruses — herpes, cytomegalo, dengue, hepatitis A, B and non-A non-B, rota, influenza, parainfluenza, respiratory syncytial and retro viruses, particularly HTLV 111. Viral infections of the G.I. and respiratory tracts are major killers of young children, particularly in third world countries. There is still concern that an influenza reassortant virus might arise which could cause a pandemic Dengue and the hepatitis viruses are major pathogens in tropical countries, particularly in South-East Asia.