Ric Saludo’s CenSEI colleague Victoria Fritz contributed this column
The virus kills one in every four people infected: 31 dead among 128 patients in China and Taiwan. That’s the grim statistic on the avian influenza microbe A(H7N9), compiled and calculated by the United States Centers for Disease Control and Prevention (CDC), the World Heath Organization (WHO), and Chinese medical authorities between mid-February and early May.
“This is an unusually dangerous virus for humans,” WHO assistant director-general for health, security, and the environment Keiji Fukuda told CNN. H7N9, he added, was “definitely one of the most lethal influenza viruses that we have seen so far.” The big question, of course, is: Will the new bug spawn another killer pandemic like the 2003 SARS outbreak? Better hold your breath, cover your mouth, and wash your hands, just in case.
In fact, the H7 strain—but not its H7N9 variety—has been turned up all over the world. WHO has traced the epidemiology of the virus. According to its April 5 report, human infections with other subgroups of H7 virus have been reported in North America, Mexico and some countries in Europe. The infections were also related to poultry outbreaks, usually resulting in mild upper respiratory symptoms. However, none of them were with H7N9.
China is the first country to report cases of H7N9 infection. The laboratory-confirmed cases come from several provinces in eastern China, with no apparent link between them. All patients became severely ill, and two family clusters had been reported. WHO was investigating the source of infection and mode of transmission, but could not link cases to an outbreak of disease among animals. The virus was eventually found in a pigeon market in Shanghai.
The April WHO report said H7N9 infection led to severe pneumonia with fever, cough, and shortness of breath, and may require intensive care and mechanical ventilation. In a May 2 briefing, Professors Wendy Barclay and Peter Openshaw and Dr. Mike Skinner of London’s Imperial College of Science, Technology and Medicine, cited salient features of the virus.
Dr. Barclay said that unlike the earlier avian flu H5N1, the H7N9 does not kill infected chickens. That makes it harder to detect the source of the pathogen. And among many people exposed to infected live birds, only a very small proportion develop the disease. Human infection occurs mostly in older males. Scientists are eager to know why.
Professor Openshaw finds this finding very worrisome. Physicians are confronted with an overwhelming disease that does not respond to available medication. The disease then quickly progresses into multi-system failure with a high mortality rate. And while the outbreak is limited to some regions for now, Openshaw is seriously concerned to see more than 100 new cases in a short period of time.
The possibility of human-to-human transmission is the source of greatest worry for scientists. Dr. Barclay said two of the mutations needed to make it human-transmissible are present in the current H7 virus. One is in the H7 component itself of the H7N9 virus, which helps the virus bind better with the human respiratory tract. The other mutation allows the virus to easily replicate after it has crossed from fowl to people.
Five mutations were needed for the previous H5N1 virus to become transmissible between humans. It appears that H7N9 needs more than the current two mutations to jump between people. But it isn’t clear what other genetic changes H7N9 requires for human-to-human infection. Bottom line: the virulent mutations can happen anytime, like the ones that enabled the microbe to bind to human cell receptors, and to grow at temperatures close to human body temperatures, which are lower than that of birds.
The WHO also admits there is no vaccine yet for H7N9 infections in humans. On a positive note, viruses from the first cases have been isolated and characterized—the first step in developing a vaccine. Moreover, there is little experience in using currently available influenza antiviral drugs on H7N9 patients. In short, there is no verified cure yet.
With the low number of cases in China, the WHO does not recommend a travel or trade ban on China. For one thing, in among the many contacts of those infected, none developed the disease.
Still, the Philippines has issued a ban on imports from China of domestic and wild birds and their products. These include day-old chicks, eggs and poultry semen. The Agriculture Department also ordered the stoppage and confiscation of all shipments of poultry and related products from China.
Last September, the National Disaster Risk Reduction and Management Council, (NDRRMC) had joint pandemic drills with the US Marine Corps in the Pacific and the International Medical Corps, a US non-government organization. The exercise was held to assess and improve the country’s readiness in the event of a pandemic.
After the exercise, International Medical Corps reported that Philippine preparedness and response planning for severe pandemics would no longer be thought of exclusively as a public health issue under state control. Rather, all sectors are now involved, with the government’s national policy framework to enable and encourage proactive, multi-sectoral pandemic planning that can be tapped in the event of a severe global health crisis.
That’s well and good and laudable, but it will take time to even set up the envisioned public-private anti-pandemic system, let alone get it working smoothly. Meantime, H7N9 and other microbes are mutating, spreading and killing.
(Updated excerpt from The CenSEI Report on the H7N9 avian flu outbreak and containment. For the full report with online research, email firstname.lastname@example.org.)