New Pandemic Flu Swine

The infecting strain was found to be a novel swine influenza virus, raising concerns that a new pandemic might occur. In response, public health officials began a massive public vaccination program.

Up to 25% of people in the United States were vaccinated. Unfortunately, the 1979 vaccine was associated with cases of Guillain-Barré syndrome, a serious neurological condition, with the risk estimated to be one to nine excess cases per million doses.

Importantly, the 1979 strain never spread, and there was no epidemic. In retrospect, the virus had a very low potential to spread from person to person. Cases outside of Fort Dix were uncommon.

The lessons learned from the 1979 swine influenza event have been applied in dealing with pandemic threats including the severe acute respiratory syndrome (SARS) outbreak of 2003.

Key aspects include ensuring adequate communication with the public, a rapid but measured response to potential threats, and ensuring that any new strain fulfills criteria to cause a pandemic before large-scale vaccination is undertaken.

Swine were first reported to have influenza-like illness during the 1918 flu pandemic. Swine influenza did not cause the 1918 pandemic. Rather, pigs apparently acquired the infection from humans or from an undiscovered source.

In 1930, the swine influenza virus was isolated and identified. For more than 50 years, the swine virus remained relatively stable and unchanged. In the 1990s, however, swine influenza viruses became more diverse, and new variants appeared.

The reason for this change is not clear, but may be related to over-crowding on large swine farms and the evolutionary pressure from swine influenza vaccines.