A potential pandemic virus would have three hallmarks. It would be of a new type to which large numbers of people would have no immunity. The illness it causes would be serious and life threatening, and it would be capable of spreading quickly from person to person.
A major question is whether epidemics are rare accidents or whether they could be started deliberately. It is possible that, by a deliberate selection of mutants or through recombinants, highly virulent and spreading strains could be obtained. By 1998, research had shown that many new highly virulent forms of influenza arise due to antigenic shift. The antigens of the influenza change, either through mutation or through assembly of a new combination of animal viruses. Ducks can store both bird viruses and some forms of swine flu virus, and some of these in combination can infect humans, such as the modern H5N1 (Hong Kong 1968) virus. Thus epidemics can be due to accidents, but it is highly likely that such accidents will continue to occur frequently.
As early as the 14th century plague panepidemic (1,348 dead in Venice, 1,377 in Rausa, and 1,383 in Marseilles), it was recognized that the transportation of people and goods was associated with the transmission of disease (12). The early practice of "quarantine" (to hold for 40 days) was in response to this recognized threat, and eventually led to the adoption of the [International Sanitary Regulations] by the World Health Assembly in May 1951. In the last 45 years, significant changes in travel and transportation have occurred: more people are travelling, there are usually more individuals on a single conveyance, travel times are shorter, and distances travelled are greater, particularly by air. People are also travelling to more varied and exotic destinations.
In the 1960s, communicable diseases that can spread epidemically were played down by health authorities because it was assumed that new antibiotics, better vaccines and improved sanitation would eradicate them. In fact, new microbes have emerged, and well-known illnesses are not under control; they are re-emerging.
The rise of AIDS in Kalingrad, Russia in 1997 has been epidemic. In 1996 28 people were known to have been infected, including 5% of the prostitutes. One year later there were over 1,850 cases of HIV, and 85% of the prostitutes had been infected. Drug abuse is common, and people deny AIDS is a problem, as they have not seen sick AIDS victims.