News Scan for Feb 20, 2018

Earlier H3N2 VE problems
Kratom Salmonella outbreak
More Lassa fever in Nigeria
H1N1 flu surge globally
H5N6 avian flu in Sweden
Gauging airborne flu spread

Immune history, not egg-based problems may have affected 2012-13 flu VE

As researchers work on solving the complex puzzle of all the factors that influence flu vaccine effectiveness (VE), researchers today report that low VE of the H3N2 component during the 2012-13 flu season may have been due to poor immune response rather than adaptations in egg-grown vaccine viruses, as previously thought. A team from the University of Chicago, Harvard University, the University of Pennsylvania, Duke University, and the J. Craig Venter Institute reported its findings today in Clinical Infectious Diseases.

That season, the VE for the H3N2 component was estimated at 39%, and during that same season, tests on ferrets immunized with the egg-adapted strain had antibody responses that reacted poorly with circulating H3N2 strains, hinting that egg adaptations were the cause of the drop in vaccine protection.

In the new study, however researchers analyzed blood samples from people who were vaccinated during the 2012-13 season and found no differences in antibody responses to the vaccine and the circulating strains.

Sarah Cobey, PhD, the study's lead author and assistant professor of ecology and evolution at the University of Chicago, said in a press release from the school, "Egg adaptations have variable effects. Sometimes they matter and sometimes they don't, but what seems to make the most difference is immune history."

A 2017 study by some of the same authors found that egg adaptations were linked to mismatches in the most common vaccine formulation for the 2016-17 flu season, and some experts suspect the problem could play a similar role in blunting the vaccine's protection against H3N2 this season.

Cobey said more basic research is needed on how to prompt responses to the right sites on the virus, which will require a better understanding of "original antigenic sin," a hypothesis that the first influenza A virus encountered in childhood strongly influences later responses to similar viruses. "We also need to understand why the vaccine appears to be bad at eliciting responses in some people some of the time. Is there really no response, or are we just not looking in the right places?"
Feb 20 Clin Infect Dis abstract
Feb 20 University of Chicago press release


Multistate Salmonella outbreak linked to kratom supplements

A plant used as a stimulant supplement and herbal alternative to opioids is connected to a multistate outbreak of Salmonella I 4,[5],12:b:- illness, the Centers for Disease Control and Prevention (CDC) announced today.

Kratom, also known as Thang, Kakuam, Thom, Ketom, and Biak, is a plant used as both a stimulant and opioid substitute. So far 28 people in 20 states have fallen ill after consuming kratom in pills, powder, or tea. No specific brand has been identified at this time, the CDC said.

Investigators are using PulseNet, the national subtyping network, to identify other illnesses that may be part of the outbreak, and whole-genome sequencing on samples from sick patients shows that isolates are closely related, suggesting a common infection source. Tests on samples from five people did not identify any antimicrobial resistance patterns.

Eleven out of the 28 patients have been hospitalized, but there have been no deaths. Symptom onset has ranged from Oct 13, 2017 to Jan 30, 2018. More than half of the patients (16) are male, and ill people range in age from 6 to 67 years old. Eight of the 11 people interviewed said they consumed kratom products in the week prior to getting sick.

"At this time, CDC recommends that people not consume kratom in any form," the CDC said. "The investigation indicates that kratom products could be contaminated with Salmonella and could make people sick."
Feb 20 CDC announcement


Nigeria's Lassa fever total grows by 19 new cases

The World Health Organization (WHO) Regional Office for Africa said there were 19 new cases, including 6 deaths, reported last week during Nigeria's ongoing Lassa fever outbreak.

Between Jan 1 and Feb 11 of this year, there have been 615 suspected Lassa fever cases, and 57 deaths, with a case-fatality rate of 9.3%. Of the suspected cases, 193 have been confirmed, of which 47 were fatal. In confirmed cases, the case-fatality rate is 23.9%.

Though Lassa fever is usually transmitted to humans by rats, 14 health care workers have contracted the disease from sick patients during this outbreak. Four of the health care worked have died.

Lassa fever is endemic in Nigeria, but this outbreak is unusually large in size, the WHO said. The virus, which can cause hemorrhagic symptoms that mimic Ebola, is spread through contact with infected rats or via the bodily fluids of an infected person.

"The ongoing Lassa fever outbreak calls for greater attention," the WHO said. "The national authorities and partners need to act quickly to prevent further spread of the disease within the country and to other countries in the region."

As of Feb 12, the WHO had deployed six experts in viral hemorrhagic fevers and 14 support staff to help the Nigerian Centre for Disease Control during this outbreak.
Feb 16 WHO African Regional Office update


H1N1 outpaces H3N2 in latest global flu report

According to a WHO global flu update today, flu is still very active in the Northern Hemisphere, with influenza 2009 H1N1 now outpacing H3N2 alongside rising influenza B activity.

In general, influenza A strains made up 55.2% of lab tested specimens. H1N1 was found in 58% of all influenza A laboratory samples last week, while H3N2 made up 42%. Influenza B, which accounted for 44.8% of specimens, has been rising steadily in the last few weeks, the WHO said, typical at this point in the season. The vast majority of influenza B specimens (92.5%) belonged to the Yamagata lineage, with 7.5% the Victoria lineage.

Flu activity remained high in Canada, Mexico, the United States, and most European countries. Influenza A has dominated North America this season, while Europe is reporting more influenza B. Though hospitalizations still remain high, there are some indicators across the United Kingdom that flu has peaked. Flu activity remains high, however, in northern and eastern European countries.

Influenza also remained high in North Africa, where 2009 H1N1 is the dominant strain. Activity also remained elevated throughout most of East Asia, where influenza B and 2009 H1N1 viruses predominated.

Flu activity was low throughout most of the Southern Hemisphere, including Southeastern Asia and South America. In the Caribbean and Central American countries, influenza activity remained low in general, except for Puerto Rico, which had high activity H3N2 and B viruses co-circulating.
Feb 20 WHO update


H5N6 avian flu detected in Swedish wild bird

Sweden today became the latest country to report highly pathogenic H5N6 avian flu this season, with the agriculture ministry reporting a detection in a white-tailed eagle found sick on Jan 28, according to a notification from the World Organization for Animal Health (OIE).

The bird was found in a nature park in Blekinge County, located in southern Sweden. It died on Feb 1, and samples were sent to the National Veterinary Institute on Feb 13, where the H5N6 finding was confirmed.

Today's report did not say if the virus is the same reassortant that was recently detected in other European countries, mainly in wild birds, and a few Asian countries.
Feb 20 OIE report on H5N6 in Sweden


Study chamber offers snapshot of airborne flu spread in ferrets

A research team based at the University of Hong Kong described a transmission chamber that allowed them to measure and characterize airborne particles involved in flu transmission in ferrets, which they say could help study the transmission of other respiratory pathogens. The group reported their findings today in Proceedings of the National Academy of Sciences (PNAS).

Scientists have been working to clarify the role of contact, droplet, and airborne transmission in the spread of flu and other diseases. The new transmission chamber separates virus-carrying particles by size and helps experts determine the sizes involved in airborne spread among ferrets.

The researchers found that transmission between ferrets occurred by large and fine particles 1.5 micrometers or larger. When they assessed transmissibility of 2009 H1N1 and H3N2 viruses, they found that smaller particles may play a more important role in spread among ferrets than seasonal H3N2, hinting that strains might vary in their transmission modes.

Overall, the findings added more evidence that flu transmission among mammals can occur by droplets as well as fine droplet nuclei. Transmission among ferrets was most efficient before fever onset and continued for 5 days after inoculation.
Feb 20 PNAS study

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