FLU NEWS SCAN: Twitter flu tracking, PAHO flu update, non-reassorting flu virus

May 5, 2011

Twitter traffic useful as flu surveillance tool
A sophisticated analysis found that surveillance based on Twitter traffic during the 2009 H1N1 pandemic can track users' interest and concerns and estimate disease activity in real time, about 1 to 2 weeks faster than other systems. University of Iowa researchers began collecting Twitter "tweets" with flu-related terms on Apr 29, 2009, and mapped them using Google Maps. In October 2009 they began collecting flu-related tweets with a new tool and expanded their search to include more vaccine-related terms.  The two data sets included more than 5 million tweets. They used an estimation model to gauge the contribution of each flu-related term. They found that interest in antivirals seemed to wane when it became clear most cases were mild, and that traffic about hand hygiene and other protective measures seemed to follow federal health messages. Twitter traffic followed the epidemic curve of the pandemic nationally and regionally. Researchers concluded that Twitter-based surveillance systems can be a cost-effective supplement to traditional systems, especially in the United States and other areas of high usage.
May 4 PLoS One abstract

Few flu hot spots reported in the Americas
Flu in the regions covered by the Pan American Health Organization (PAHO) is mainly declining or circulating at low levels, with other viruses such as respiratory syncytial virus (RSV) responsible for the bulk of flu-like illnesses in some locations, according to an update yesterday. The percentage of respiratory samples testing positive increased in Mexico, with most of it the 2009 H1N1 virus. Flu activity increased in some Caribbean countries, but the predominant strain has varied among locations. In Central America, the percentage of samples that yielded respiratory viruses remained low, though Costa Rica saw in increase, mainly from adenovirus and parainfluenza. The respiratory illness situation varied in South American countries. For example, respiratory virus levels were low in Colombia and Paraguay, with RSV the predominant virus. In the United States and Canada, flu levels continued to decline, with influenza B accounting for the greatest proportion of flu viruses in Canada.
May 4 PAHO flu update
In other flu developments, the US Centers for Disease Control and Prevention (CDC) yesterday issued flu information for travelers, noting that though flu activity is low in the United States during the summer, the viruses can circulate at high levels in other parts of the world during those months. It urged travelers who have not been vaccinated during the US flu season to get immunized before departing, especially those at high risk for flu complications and those who will be traveling with large tourist groups, such as on cruise ships. The CDC warned travelers that flu vaccines made for the 2010-11 season expire in June and that the new version of the vaccine won't be available until the fall. The CDC also urged travelers to check flu activity ahead of time in regions they will be visiting and follow hand hygiene and other precautions during the trip.
May 4 CDC flu advice for travelers

Scientists create live-virus flu vaccine that can't mix with other strains
Scientists report that they have created a live-virus influenza vaccine that won't reassort with other flu viruses, eliminating what they say is a possible hazard associated with the existing live attenuated influenza vaccine. To achieve this, the researchers exploited the inability of influenza A viruses to reassort with type B viruses, according to a report in the Journal of Virology. They created a weakened type B virus that contains a portion of the hemagglutinin protein from a type A virus. The hemagglutinin genetic material in the recombinant virus was modified so that it contained "influenza B packaging signals, and therefore cannot be incorporated into a wild-type influenza A virus." Using this method, the scientists created influenza B viruses containing hemagglutinin components from H1N1, H3N2, and H5N1 strains. The recombinant viruses were all attenuated, and they protected mice from otherwise lethal influenza A infections, the report says.
May 4 J Virology abstract

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