AHEAD IN 2015: VIRUSES, EPIDEMICS AND UNITED NATIONS HAGGLING—PART TWO: Flu Strikes in Many Virulent Forms Across the World
The United States is now officially in the grips of an influenza epidemic, according to the CDC, caused primarily by a strain of H3N2 flu that is not akin to the form used in this year’s vaccine development. As a result, immunization is expected to offer protection against the other two or three strains in circulation, and may shorten the length and severity of disease for H3N2 sufferers, but will not prevent infection. Flu reports surged before Christmas across the Deep South and Mississippi Valley states, as shown in this CDC graphic.
The CDC has been comparing this latest H3N2 flu outbreak to the 2009 pandemic of H1N1 “swine flu,” which originated in North American pigs but spread to a few California and Texas children, and exploded in Mexico in March of that year. Fortunately the H1N1 strain was not especially virulent, but it did prove unusually contagious and swiftly spread worldwide in one of the largest pandemics in modern history. The CDC graphic below compares the current trajectory of H3N2 flu to those of recent years, illustrating why the agency is anxious about this year’s epidemic.
By New Year’s Eve thirty-six states in the United States reported unusually high volumes of flu cases and fifteen children in the country had died of H3N2. During the final week of December this new flu accounted for 6.8 percent of total deaths in the United States, based on CDC routine surveillance of mortality in 122 cities. The new flu strain, which has caught vaccine manufacturers, the WHO, and CDC by surprise, is cocirculating with other types of flu, including a return of the H1N1 strain. This puts public health leaders and physicians in a tough bind: they must find a way to encourage North Americans (the United States, Canada, and Mexico) to get vaccinated against the other strains, even though the shots are not effective against H3N2. Further muddying the public health message is the presence of so-called H3N2v (for variant)—a form of flu that arose in 2010 from Midwestern swine, spread in county fairs and through the pork industry, and can be dangerous for children. Public health messaging this year is a complicated and confusing challenge. Even when the vaccine is completely effective, it’s a tough sell in the United States, Canada, and Mexico. With so many strains circulating and one showing no response to available vaccines the post-holiday return to schools and jobs is likely to witness a dramatic surge in cases across North America.
I am pleased that the CFR-sponsored Independent Task Force chaired by David H. Petraeus and Robert B. Zoellick, North America: Time for a New Focus, drew attention to the need demonstrated during the 2009 H1N1 epidemic for full public health and scientific cooperation among the United States, Canada, and Mexico, stating:
The Task Force recommends that the United States, Canada, and Mexico develop protocols and agreements for the production and sharing of drugs and equipment to prepare for future epidemics.
The United States and its neighbors should establish real-time exchange of information about fraudulent drug investigations and outbreaks, similar to that which exists between the United States and the European Union, to better ensure the health and safety of North America’s people.
Internationally the picture is even more baffling. The H5N1 avian virus, which circulated in Asia since the mid-1990s, killing 393 of the known 668 infected humans, has returned not only in China and southeast Asia, but especially this year in Egypt, infecting domestic birds and killing ten people so far this season, including one in Cairo. And in neighboring Libya at least five people have died of H5N1 so far this season. All the current crop of H5N1 cases appear to have been bird-to-person transmission.
Also making a return in China and Asia is the H7N9 avian flu, which kills more than a third of the people it infects and also rarely transmits from person to person. This flu strain first appeared in the Shanghai area in 2013, swiftly spreading across much of both urban and rural China that winter and spring. As human cases surfaced in late December 2014, Shanghai, Hong Kong, and southern China’s Guangdong province went on public health alerts. The link between live animal poultry markets across China and transmission of H7N9 is now irrefutably demonstrated, offering hope that closing markets as soon as infected birds are discovered can prevent human illnesses and deaths. A new study from Robert Webster’s St. Jude’s team shows that H7N9 appeared in 2013 having morphed from an old chicken virus, H9N2. A crucial message from the Webster group is that influenzas do not just pop up out of nowhere—they jumble their genes up, mixing one avian or swine flu with another to form something new and potentially dangerous.
Such jumbling certainly seems to be happening on a grand scale this winter. In January 2014 South Korean authorities reported an outbreak of a new flu, H5N8, in ducks. Despite widespread bird-culling efforts, the virus persists and has spread to Russia, China, Germany, the Netherlands, United Kingdom, Italy, Japan, and last month, the United States—in all cases, in poultry and wild birds. Since November 2014 nine outbreaks of the new virus have occurred in four European countries, with none involving human cases. The North American cases began in northwestern Canada and have cropped up in Washington state and Oregon along the wild bird flyway that stretches down to Mexico and as far north as Alaska. Complicating matters in North America is the emergence of H5N2 in birds along the same flyway.
Every wild aquatic bird flyway in the world appears to be contaminated now with at least one virulent influenza strain, and some flyways host multiple influenzas. As shown in this Food and Agriculture Organization map, there are only two locations – both Arctic – where the flyways of Asia, Africa and Europe intersect with those of the Americas.
Meanwhile, another flu strain, H5N6 has surfaced in Vietnam alongside an ongoing H5N1 outbreak that has claimed human lives. The H5N6 has also surfaced in China’s Guangdong province, causing human cases, and in poultry and people in Sichuan and Harbin.
Did we mention H10N8? No? It also emerged in China in 2014 and has caused human infections, spreading from live animal markets. And a new H3N8 bird flu jumped to seals and has been killing them along North American coastlines in large numbers. Webster’s team has shown that this new mammalian killer has the genetic traits necessary to infect human lung cells, just as it does the lungs of seals.
If this dizzying array of genetic forms of heamagglutinin (H) and neuraminidase (N) influenzas has your head spinning, join the club. Surveillance has improved, so that more types of flu in animals are getting detected than was the case twenty years ago. But many scientists believe that the pace of evolution in influenza is hastening because of human movement and trade along the Asian flyway, giving more opportunities for various types of flu to comingle, jumble their RNA genetic material together, and form novel strains. This mass scale mix-and-match is making it ever harder for the WHO and scientists worldwide to predict which forms of influenza are likely to hit human populations, accurately predict what type of vaccine is likely to prove effective each year, and anticipate the zoonotic movement of flu viruses from wild birds to domestic fowl, fowl to humans, humans to swine, and swine back to human beings.