If a flu pandemic similar to the deadly one that spread in 1918 occurs, it may be possible to keep the pandemic in check through vaccinations, a new study suggests. The infamous 1918 pandemic killed up to 40 million people worldwide, but the virus strain was not unusually contagious compared to other infectious diseases such as measles, according to a new analysis by researchers at Harvard School of Public Health. However, the 1918 flu was quite lethal once contracted, believed to be 10 times more lethal than other pandemic strains.
Epidemiologists analyzed historical epidemic data in 45 US cities and found that the transmissibility of the 1918 strain as measured by the number of people infected by a single case was only about 2 to 4, making the strain about as transmissible as the recent SARS coronavirus. Since people with influenza can transmit the infection before the appearance of symptoms, strategies for transmission reduction, including vaccination, would need to be implemented more rapidly than measures for the control of the recent SARS outbreak. Isolation methods alone, such as those used for controlling SARS, would not be effective.
The analysis, "Transmissibility of 1918 Pandemic Influenza," by Christina Mills, doctoral student in the HSPH Department of Epidemiology, and faculty co-authors appears in the Dec. 16, 2004 issue of Nature.
World Health Organization officials have warned that we are closer now to another pandemic than in any other recent time because of the persistent bird flu epidemic in East Asia that threatens to jump to humans.
"Our study suggests that if you could vaccinate a reasonable number of people before exposure, a future flu epidemic could be controlled," said Mills. "But flu takes just a couple of days to become contagious in a person, unlike the almost week-long latency period we experienced with SARS. Isolation would be only partially effective. Rapid vaccination is essential."
"Before this study, estimates were all over the map on the transmissibility of pandemic flu," said co-author Marc Lipsitch, associate professor of epidemiology at HSPH. "Some thought it was so transmissible that vaccines would be unlikely to stop it. This study is optimistic, except we don't have the vaccine. It is now even more important to put resources into the development of vaccine technology, manufacture and distribution systems to make possible a rapid response to the next outbreak of an entirely new flu strain."
The problem with rapid vaccination as a response to a new strain with pandemic potential is that it takes 6 months to make a vaccine for a new virus strain and then the whole world has a capacity to make only 300 million doses. Worse yet, a completely new strain would require two doses per person for full immunity. We need vaccine manufacturing technology that is faster and more easily scalable.
In event of the emergence of a really dangerous flu strain as things stand now we aren't going to get vaccines quickly enough to prevent the spread of the virus. Therefore societies would need to be quickly reorganized and rearranged to reduce the rate of transmission of flu viruses. People would need to make many changes to how they carry out their daily routines in order to reduce the risk of exposure to influenza.
|Share |||Randall Parker, 2004 December 15 11:08 PM Dangers Natural Bio|