News Scan for Aug 20, 2014

Influenza B vaccine mismatch
US chikungunya count rises
Nut butter recall
Seals as ancient TB carriers

12-year study finds 42% of flu B cases involved strains not in vaccine

Researchers who sifted data from 12 recent influenza seasons in Finland concluded that about 42% of influenza B cases involved strains that were not targeted by the vaccine, which they say supports the inclusion of both influenza B lineages in seasonal flu vaccines.

Influenza B viruses belong to two lineages, Victoria and Yamagata, which fluctuate unpredictably from year to year, making it difficult to decide which lineage to include in trivalent flu vaccines. Because of this, several manufacturers introduced quadrivalent vaccines containing both B lineages in the United States about a year ago.

The researchers analyzed all available Finland-wide data on confirmed flu cases recorded between Jul 1, 1999, and Jun 30, 2012, except for the H1N1 pandemic season (2009-10), according to their Aug 19 report in Clinical Infectious Diseases. Data were drawn from the Infectious Diseases Register and the National Influenza Center of Finland's National Institute for Health and Welfare.

Of a total of 34,788 cases, 74.0% were influenza A and 26.0% were influenza B. From the type data available, the authors estimated that 41.7% (3,750 of 8,993) of B cases were caused by viruses from the lineage not included in the vaccine that year. The authors classified the match between circulating B strains and the vaccine B strain as good in 7 of the 12 seasons and poor in 4 of the 12.

"Altogether, opposite-lineage influenza B viruses accounted for 10.8% of all influenza infections in the population, the proportion being highest (16.8%) in children aged 10-14 years and lowest (2.6%) in persons aged 70 years or older," the report states.

"The population-level impact of lineage-level mismatch between the vaccine and circulating strains of influenza B viruses is substantial especially among children and adolescents," the authors conclude. "The results provide strong support for the inclusion of both influenza B lineages in seasonal influenza vaccines."
Aug 19 Clin Infect Dis abstract


US tally of travel-related chikungunya cases reaches 636

The trickle of travelers returning to the United States with chikungunya infections has continued over the past week, with the count for this year reaching 636, or 56 more than a week ago, the Centers for Disease Control and Prevention (CDC) reported today.

All but a handful of the cases—628—were reported in people who had visited the Caribbean or South America, the CDC said. The current epidemic in the Caribbean and neighboring parts of South America reached nearly 586,000 cases as of Aug 15.

Other travel-related chikungunya cases in the United States included five in people who visited the Pacific and three in travelers to Asia—the same numbers as last week. Another four cases, all in Florida, were locally acquired, putting the overall US total for this year at 640 cases in 43 states and Washington, DC.

The case count for Puerto Rico and the Virgin Islands stayed the same this week, according to the CDC. Puerto Rico has had 16 travel-linked and 201 locally acquired cases, while the US Virgin Islands has had 2 of each.

In the 8 years before the Caribbean epidemic (2006 through 2013), an average of only 28 chikungunya cases were reported annually in the United States. The disease is not nationally notifiable, but cases can be reported to ArboNET, the national surveillance system for arthropod-borne diseases.
Aug 19 CDC update
Related Aug 18 CIDRAP News item
Related Aug 13 CIDRAP News item


Illness reports, testing prompt nut butter recall

A firm known as nSpired Natural Foods Inc. has recalled its peanut butters and almond butters because of possible Salmonella contamination, according to a company notice released yesterday by the US Food and Drug Administration (FDA). The company said it became aware of the risk through routine FDA testing and reports of four illnesses that might be linked to the products.

The recall applies to certain lots of Arrowhead Mills peanut butter and MaraNatha almond and peanut butters. Some are private-label brands sold by Kroger, Safeway, Trader Joe's, and Whole Foods. The products were distributed across the United States, Canada, Hong Kong, United Arab Emirates, and the Dominican Republic. The items were also sold online.

The 42 items on the recall list have a variety of best-by dates, but all except for three Whole Foods products extend into 2015.

Peanut butter products have been linked to Salmonella outbreaks before. In 2009 a Salmonella Typhimurium outbreak linked to peanut butter from the Peanut Corp. of America sickened at least 714 people in 46 states. The most recent outbreak, in 2012, involved peanut butter made by Sunland Inc. That outbreak involved Salmonella Bredeney and sickened at least 42 people in 20 states.
Aug 19 FDA press release


Seals, sea lions may have spread TB to Americas 1,000 years ago

An international research team that examined genetic samples from across the world for DNA evidence of tuberculosis (TB) today described surprising findings: that sea lions and seals probably carried the disease to South America at least 1,000 years ago—well before European explorers arrived. The team published its findings today in Nature.

The DNA analysis covered modern Mycobacterium tuberculosis genomes that included animal strains and some from 1,000-year-old human skeletons found in Peru. Anne Stone, PhD, an anthropologist at Arizona State University (ASU) and one of the team's leaders, said in a National Science Foundation (NSF) press release that the findings provide strong evidence pointing to marine mammals as the likely culprits.

"What we found was really surprising," she said. The authors found a clear relationship between the Peruvian TB samples and animal TB lineages, especially those from seals and sea lions, said the NSF, which partially funded the study.

Because of the wide variety of TB strains in Africa, scientists speculate that the pathogen originated and spread from there, according to the NSF release. The authors suggest that humans passed the disease to animals, including seals and sea lions, in Africa, and that the animals carried the disease to South America, where they gave it back to humans.

The authors hypothesize that after European TB strains arrived in the Americas, they completely replaced the prior strains brought over by marine mammals.

Johannes Krause, PhD, a paleogeneticist from the University of Tubingen in Germany who co-led the study, said in the release that the connection to seals and sea lions would explain how a mammal-adapted pathogen that evolved in Africa about 6,000 years ago could have reached Peru 5,000 years later.

The team said it still hopes to determine when the more virulent European TB strains replaced the earlier strains and learn more about how the European strains affected native populations in the Americas.
Aug 20 Nature abstract
Aug 20 NSF press release
Aug 20 ASU press release

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