Are we heading for a bird flu pandemic? Experts weigh in – Boston.com
By Abby Patkin While bird flu’s risk to the general public remains low, there are many “barriers to success” that make containing the virus — and staving off a possible pandemic — somewhat tricky for public health officials, according to a Boston-based infectious disease expert.Recent cases of avian influenza, or H5N1, among U.S. farmworkers have been overwhelmingly mild, but also “curious and poorly understood,” said Dr. Shira Doron, chief infection control officer for Tufts Medicine and hospital epidemiologist at Tufts Medical Center. Speaking to reporters at an Infectious Diseases Society of America briefing last week, Doron noted the 66 confirmed human cases logged by the U.S. Centers for Disease Control and Prevention over the past year are “certainly an undercount, since we’re unlikely to be capturing some cases of mild disease.” Likewise, she said, the H5N1 fatality rate — about 49% globally in all confirmed cases since 2003, per the World Health Organization — is “surely a huge overestimate, since people with mild illness generally don’t get tested.” Yet Doron also pointed to more severe cases among three recent patients in North America. The U.S. hit a grim milestone with its first human bird flu death last week, a Louisiana senior who had been hospitalized with severe respiratory symptoms.Dr. Julio Figueroa, chief of infectious diseases and professor of clinical medicine at Louisiana State University Health New Orleans, noted the man who died had underlying medical conditions that put him at higher risk. “What is also known is that it was likely related to the intersection between wild birds and a backyard flock that the individual had at the home with some sick birds, and that the strain is one of the bird strains, not the one that’s associated with the cattle transmission that is going on in California,” Figueroa said during the briefing. Both Figueroa and Doron pointed to the lack of documented human-to-human spread.“Analysis of the strains that are circulating today show them to be poorly suited for transmission between humans, and so poorly suited for pandemic potential,” Doron said. “They’re susceptible to routine antivirals like oseltamivir, or Tamiflu. They’re well matched with a couple of candidate vaccines the U.S. already has in its stockpile, which have been shown to be safe in humans.”However, she asserted the virus’s relatively minor spread among humans thus far — coupled with the possible logistical challenges of deploying a bird flu vaccine to farmworkers — renders mass vaccination efforts premature.“Those infections have still been very, very mild, and all vaccines have side effects, and we are in an era of vaccine skepticism, and we don’t necessarily want to be deploying a vaccine when it isn’t absolutely necessary,” Doron said. Still, she cautioned that higher-risk populations such as poultry and dairy workers should take precautions like wearing protective equipment and practicing “meticulous hand hygiene.” Seasonal flu vaccination is more important than ever, she added.“It’s never a good idea to drink unpasteurized milk, but now is an especially bad time to do so,” Doron said. According to Doron, current bird flu strains would have to undergo several changes to increase the possibility of a pandemic.“In order to be more suited for human infection and human to human transmission, and thus pandemic potential, a number of mutations would have to occur,” she explained. “The virus would have to be better at binding to human airway cells than it is right now.”Doron acknowledged a Canadian teenager who recently developed a severe case of bird flu was found to have virus mutations, though she said it wasn’t clear whether those mutations happened before or after the teen became ill.In his “Inside Medicine” newsletter last week, Dr. Jeremy Faust — a public health researcher and emergency physician at Brigham and Women’s Hospital — explained how flu season raises the likelihood of co-infection, where someone might contract both seasonal influenza and bird flu at the same time. In those cases, the two kinds of flu could mix together to form a new, possibly more potent, variant. “We don’t know what our overall odds of a pandemic are right now. But we roughly know the odds of a co-infection with pandemic potential, and they will be uncomfortably high in the coming weeks,” Faust wrote. “We also know how to alter the odds in our favor. Are we doing all we can?”And if things take a turn for the better, how long before the bird flu outbreak begins to peter out?“I think it really is going to depend on how long immunity lasts, and it’s too early in the outbreak to know that,” Doron said. If immunity from the virus lasts only a few months, she added, “then we could have ongoing spread indefinitely.”She described many “barriers to success” in public health officials’ efforts to contain the outbreak.“One of them is, we still don’t really fully understand how the virus got into the dairy herds in the first place, how exactly it is spreading between cows and from farm to farm,” Doron said. “That mechanism has not been well established, and if you don’t know how it’s spreading, that makes it very hard to control the spread.”She emphasized the importance of pandemic preparedness and partnership between agencies that oversee agriculture, wildlife, and public health.“I think it needs to be said that there’s … always a potential for this virus to become a pandemic, but there’s also the potential for any existing — or not yet existing — virus to become a pandemic,” Doron said. “So we need to maintain that pandemic preparedness across the board, not just focusing on H5N1.”Abby Patkin is a general assignment news reporter whose work touches on public transit, crime, health, and everything in between.Sign up to receive the latest headlines in your inbox each morning.Be civil. 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