Influenza viruses can spread quickly, and many of the public health measures that have been taken in recent years have focused on limiting the viruses' transmission through quarantine-style methods. But new data shows the approach may not be very effective. When studying the 1889 "Russian" influenza pandemic, scientists found that the virus was able to spread rapidly across the ocean despite the limited travel of that era.

The way the word "pandemic" seems to be thrown around, you wouldn't know it's fairly rare for an illness to achieve that designation. Since the early 18th century, there have only been 11 viruses that qualify for "pandemic" status, including the most recent spread of the OSIV/H1N1 virus. Only a handful of these pandemics haven been studied, including the 1957, 1968, and 1918 flus. Scientists knew the so-called Russian pandemic of 1889 could be important, but were only recently able to get good data on it, through sources like those that tracked the spread of influenza among various European armies.

There were surprising similarities between the 1889 pandemic data and that of the heavily studied 1918 pandemic. In 1889, the virus spread from Russia through Europe and over to North America over the course of only four months, and had an infection rate similar to the 1918 pandemic, with about two new hosts per sick person. However, the mortality rate from the flu in 1889 was only a tenth of that in 1918.

Scientists also realized that, despite much slower travel in the 19th century, the flu was able to spread almost as quickly as it can today, suggesting that there is a trade-off related to how quickly people move around. Someone carrying the virus can infect fewer people in many places, or many people in fewer places; either way, the virus spreads at more or less the same rate.

This supports mathematical models that show that restricting air travel and similar tactics do little to stop flu spread; if the 19th century flu could do without aircraft, so could the 21st century version. To contain influenza, researchers suggest that we would do better to tailor our methods to the population profile of individual cities, rather than trying to lock them down.

PNAS, 2010. DOI: 10.1073/pnas.1000886107 (About DOIs).