Study Details Swine Flu Transmission Rates

Aug. 29 -- FRIDAY, Aug. 28 (HealthDay News) -- Every person who is infected with the H1N1 swine flu puts 1.5 other people at risk over the three days before coughing, fever and other symptoms appear.

That's the conclusion of a new study published in the journal Influenza and Other Respiratory Viruses.

Anyone showing early symptoms of the flu needs to contact their health-care provider immediately. In addition, anti-viral drugs will likely help slow transmission, the researchers said.

The currently circulating swine flu first appeared in the town of La Gloria in Veracruz state in Mexico apparently sometime in early March. By March 15, it had spread to Mexico City and, since then, to much of the world.

According to the latest World Health Organization (WHO) figures, more than 209,400 cases of swine flu have occurred globally, with at least 2,185 deaths. These numbers likely underestimate the outbreak, WHO noted.

The authors of the new study looked at Mexico City data on all suspected cases of H1N1 swine flu from April 15 to April 25, examining people they had been in contact with, and cross-referencing that information with the onset of symptoms, hospitalization and other factors.

Their conclusions: The 2009 H1N1 virus is spreading at a rate comparable to the 1957 and 1968 flu pandemics -- the most recent pandemics prior to this year's swine flu -- and to the SARS (Sudden Acute Respiratory Syndrome) outbreak, which surprised the world in 2003.

"Even if flu has a reproduction only a little bit above 1 [in this case 1.5], it has its effect because, in a susceptible population, it can start jumping from person to person within one to two days," said study co-author Dr. Nathaniel Hupert, co-director of Cornell University and Weill Cornell Medical College's joint Institute for Disease and Disaster Preparedness. He is also director of the Centers for Disease Control and Prevention's Preparedness Modeling Unit.