H5N1

Branswell on problems with H3N2 flu vaccines (updated & corrected)

Update: Thanks to Helen Branswell for correcting me on this story: it's not just about this year's vaccine, but a more general problem. Via The Boston Globe, Helen Branswell writes: Researchers find weak link in flu vaccine. Excerpt:

The reputation of the flu vaccine has taken a bit of a beating in recent years. Official claims about its effectiveness have been downgraded. And some years – like last year – the vaccine hasn’t been well-matched to the influenza viruses making people sick. 

Now research points to a single component as the weak link in the vaccine, which is actually designed to protect against three or four types of influenza viruses. 

Data being presented at a infectious diseases conference in San Diego this week show that the part of the vaccine targeting a strain known as influenza A H3N2 has cut the risk of infection by an average of only 38 percent in recent years. 

The new research suggests the vaccine offers substantially stronger protection against the H1N1 subtype and influenza B – cutting the risk of infection by 60 percent to 75 percent. 

The relative weakness of the vaccine against H3N2 is problematic, and not only because it has the potential to erode public confidence in the vaccine overall. As a family, H3N2 viruses cause more severe illness. When these viruses dominate, flu seasons are typically severe. 

“H3N2 is clearly where we have the biggest problem and that’s also of greatest concern because H3N2 is the virus that accounts for most of the hospitalization and mortality in seniors,” said Dr. Edward Belongia, an influenza epidemiologist at Marshfield Clinic Research Foundation in Marshfield, Wis.

Coston: It’s not just Ebola

Via his blog Avian Flu Diary, Mike Coston reminds us It’s Not Just Ebola. This is a summary of other disease threats we face, documented with many links. Excerpt:

And of course, to this rogues gallery of pandemic threats you can also add any number of influenza subtypes in the wild (including old pandemic viruses like H2N2 and H3N8), the growing ranks of antibiotic resistant bacteria which could prove every bit as deadly as a pandemic, and Virus X . . .  the one that isn’t on our radar, yet.   

The point here is that once Ebola is contained (I remain cautiously optimistic that it will be, but fully expect it to exact a horrendous cost) the threat posed to global public health by these emerging diseases doesn’t go away. If anything, with our growing population and increasing mobility, the threat grows greater with each passing year.   

If fact, we will be lucky if another shoe doesn’t drop this winter while our international efforts are focused primarily on West Africa.

Pandemic potential of emerging influenza

Via The Lancet Infectious Diseases, an editorial: Pandemic potential of emerging influenza. Excerpt:

Throughout the 20th century, four pandemics primed our current approaches to influenza surveillance. The 1918—20 pandemic was by far the most devastating on a global scale. At the end of World War 1, with many parts of the globe reeling from enormous loss of life, this particularly severe illness was caused by influenza A H1N1, with high rates of haemorrhage adding to the pneumonia death toll—the disease is estimated to have killed upwards of 50 million people with a particularly high death rate among young adults. 

The next four pandemics—H2N2 in 1957—58, H3N2 in 1968—69, and a much milder H1N1 in 1977—78—were less severe than the 1918—20 event, no doubt mitigated in part by improvements in health care and the development of vaccines, but the threat of a global pandemic lingers. 

The 2009 pandemic was a truly modern affair: the case count was delivered to the world's media in real-time from the first seven cases identified in the southwest USA, the spread of the disease, facilitated by the ease of global travel, was monitored with near daily updates of confirmed cases. 

The 2009 influenza A H1N1, like the 1918—20 virus, disproportionately affected young adults, but was less severe, causing an estimated 300 000 deaths in the first year. The 2009 pandemic aside, the influenza strains that have dominated research and the news in recent years behave very differently to the pandemic viruses of the 20th century. They are the particularly severe avian viruses, which thankfully rarely infect human beings, but when they do, they have exceptionally high case fatality. 

Highly pathogenic avian influenza H5N1, first identified in Hong Kong in 1997 and circulating more widely since 2003, has been recorded in 649 patients in 16 countries, almost 60% of whom have died. The predictions for a pandemic caused by this virus were terrifying, but despite research showing that the virus can become transmissible in mammals with just a few mutations, it remains an avian virus that only very rarely affects people who have had close contact with infected poultry. The pathogenic effect of this virus on poultry also enables early warning. 

By contrast, H7N9, identified in March 2013, does not cause illness in infected poultry, making it hard to detect before people become sick. Despite the recent surge in the number of cases, the disease remains confined to China (including Hong Kong and Taiwan), and closure of so-called wet markets seems to be fairly effective in halting its spread. 

Influenza viruses are some of the most dynamic pathogens, and their changeable nature makes them fascinating subjects for research. A key question for people investigating and tracking the emergence and spread of new viruses will be whether we can predict pathogenicity and pandemic potential—and importantly, which novel strains combine both. 

Modern surveillance, typing, and sequencing technologies provide unprecedented opportunities to identify new strains among the first few human cases. We must be careful not to overstate the pandemic potential of novel strains but we should also embrace insights into pandemic potential that they afford.

CIDRAP: Flu scan for December 4

Via CIDRAP: Flu Scan for Dec 04, 2013: Hong Kong H7N9 steps; H2N2 threat assessment; Low-path avian flu outbreak. Excerpt:

Experiments involving an avian H2N2 flu virus that caused a pandemic in the late 1950s and still circulates in birds found that it can infect mammalian cells and spread in ferrets, though it lacks the genetic markers for human adaptation, according to a study in the Journal of Virology. The goal was to assess the risk of the H2N2 virus, which hasn't been seen in humans since 1968. 

Researchers from St. Jude Children's Research Hospital in Memphis analyzed 22 H2N2 viruses obtained from domestic and wild poultry from 1961 to 2008, the most comprehensive analysis so far of the virus. They found that the viruses haven't changed much since when H2N2 circulated as a pandemic strain. Most of the isolates they looked at replicated in mouse and human bronchial epithelial cells but showed little ability to replicate in swine tissues. 

Several isolates replicated well in ferrets, and three spread through direct contact in the animals. Researchers classified one of the three strains, which was isolated in 1979 from a duck in Hong Kong, as having high pandemic potential. But no ferret-transmissible H2N2 strains spread by the airborne route. 

Isolates still had a preference for cells in avian respiratory tracts, the team wrote, and the team's antiviral susceptibility tests found that all of the viruses were susceptible to neuraminidase inhibitors and adamantanes. 

Co-author Jeremy Jones, PhD, said in a St. Jude press release that although the viruses appear avian, the study found that they can behave like mammalian flu strains. "That is troubling, because some of the H2N2 pandemic viruses looked avian when the pandemic began in 1957, but in a few short months, all of the isolated viruses had picked up the genetic signatures of adaptation to humans," he said. Jones added that the pattern could recur if the viruses jump from birds to humans again. 

The group concluded that the greatest threat would be to people under age 50 who have no previous exposure to the virus. They also observed that isolates' close similarity to an H2N2 pandemic vaccine candidate could suggest that another outbreak in humans might be mitigated by a vaccine, though the changes in the virus warrant close surveillance.