H7N9: outbreak of a mysterious new strain of bird flu

In April, China took the drastic measure of shutting down 780 live poultry markets in order to stop the spread of H7N9 bird flu, a sometimes-lethal virus that had been quickly spreading. Reports of infection by the virus all but stopped following the shutdown, and researchers are now reporting that it was in fact the shutdown that caused the change. In a paper published tomorrow in The Lancet, researchers led from The University of Hong Kong report that shutting down live poultry markets brought about a "sudden and strong" 97 percent drop in the daily number of H7N9 infections in humans.

Though the correlation may seem obvious, the researchers note that prior studies hadn't explicitly confirmed that the shutdown was responsible for stopping the spread of H7N9. "Without this robust evidence, policymakers would struggle to justify further closures of [live poultry markets] because of the millennia-old culture of trading live birds and the potential huge economic loss on the poultry industry in China," Benjamin J Cowling, the paper's lead author, says in a statement. The researchers report that some have pegged the economic loss of closing the markets between April and June at more than 57 billion Yuan, or around $8 billion.

A deadly new strain of bird flu called H7N9 has killed at least 43 people and infected a total of 134, mainly in western China, according to the World Health Organization. The outbreak in humans has slowed down since the virus was first detected in March, thankfully. But things on the virology front are heating back up because today, 22 scientists from around the world announced their decision to begin new experiments on the virus, which will involve deliberately mutating it in laboratories to create more lethal, drug-resistant and easily-transmissible strains. "Although this A(H7N9) virus outbreak is now under control, the virus (or one with similar properties) could reemerge as winter approaches," the scientists write in a letter explaining their decision, published today in the journals Science and Nature.

Other scientists, though, are extremely concerned that these types of experiments to create super strains of H7N9 have the potential to break out of the lab and cause a pandemic. The backers of the experiments, lead by controversial virologist Ronald Fouchier of the Erasmus Medical Center in Rotterdam, Netherlands, argue they need to move forward and create strains that are more infectious in humans in order to know how to fight probably future mutations of this virus in the wild. As they put it in their letter:

Scientists have confirmed that the deadly H7N9 bird flu strain is transferrable between ferrets. Six of the animals — which often serve as a good measure for the risk of transmission between humans — were injected with the virus and placed in a cage with three uninfected ferrets. Three more uninfected specimens were nearby, but outside of the cage. All three caged ferrets became infected with H7N9, though only outside ferret was afflicted. That suggests there's less risk of infection by air compared with direct contact, but scientists warn the successful transfer rate is higher than many prior avian viruses. Worse yet, the National Institute of Allergy and Infectious Diseases-funded test further confirms that new carriers can appear asymptomatic for an entire day while spreading H7N9 to others. Don't start worrying about a pandemic just yet; the same test applied to pigs revealed that swine failed to transmit H7N9 through either contact or air exposure. Nonetheless, H7N9 has thus far killed 36 people and caused sickness in 131 individuals, though its spread appears to have slowed in recent days.

After months of mounting concern, Chinese health officials are breathing a sigh of relief: no new human cases of H7N9 have been reported in the country in more than a week. The milestone marks the first time since March, when the H7N9 outbreak first began, that human cases haven't continued to increase.

In the week beginning May 13, one previously infected patient succumbed to the virus, according to a statement issued on Monday by China's National Health and Family Planning Commission. That death brings the H7N9 fatality toll to 36, with 130 confirmed cases in total.

As influenzas go, the H7N9 virus at first seemed relatively benign: in late March, the Chinese government reported that three individuals had contracted the illness, and that two had died. The disturbing revelation was tempered, however, by reassurances that human-to-human transmission was highly unlikely, and that Chinese health authorities were taking unprecedented measures to monitor and contain the virus. But four weeks later, the situation has changed: 23 people are now dead, and 122 have been infected across several provinces. Officials with the World Health Organization last week warned that the virus is one of "the most lethal" they've ever seen, and appears to jump easily from birds to humans.

The progression of this virus, it appears, is still far from over. And experts already warn that bird-borne viruses like H7N9 will continue to emerge from China for the foreseeable future — largely because of a unique combination of ecological and cultural factors that make the country a hotbed for deadly avian influenzas.

Scientists in China say they have pinpointed a likely source of a new strain of avian influenza (bird flu) that's killed 23 people in the country so far: chicken sold in the markets of Zhejiang, China. In a study fast-tracked into online publication in the international medical journal the Lancet yesterday, 30 scientists from hospitals and universities around China took samples of the H7N9 virus strain from human patients and compared it to samples of viruses grown from chicken in a Zhejiang market and found that "viral isolate from the patient was closely similar to that from an epidemiologically linked market chicken." Yet the human version of the virus also seems to be a compilation of sorts: The scientists found that the H7 portion was similar to domestic ducks from Zhejiang, while the N9 portion more closely resembled viruses in wild birds in South Korea.

A new strain of avian influenza (bird flu) that has killed 22 people so far in China is "one of the most lethal influenza viruses" that scientists have ever encountered, according to Keiji Fukuda, an official with the World Health Organization (WHO). Fukuda also said of the new H7N9 virus strain that "when we look at influenza viruses, this is an unusually dangerous virus for humans," as Reuters reported today.

A recent outbreak of a new strain of avian influenza (bird flu) has killed at least 17 people in China since the first cases in humans were reported in late March. No cases of the H7N9 virus have yet been reported outside of that country, but in the US, precautions are being taken anyway. The US Centers for Disease Control and Prevention (CDC) issued new guidance to doctors and other health care workers yesterday, warning them to "consider the possibility of avian influenza A(H7N9) virus infection in persons" manifesting symptoms. Those include high fever and cough, which can quickly progress to severe pneumonia and death. The guidance also recommends treatment using specific antiviral drugs.

The CDC held a conference call with healthcare professionals on Thursday to brief them on the virus, which a spokesperson said was part of the agency's "routine preparedness measures for an outbreak with pandemic potential," as Bloomberg Businessweek reported. So far, neither the CDC nor the World Health Organization have yet said that the outbreak in China is in danger of becoming an international pandemic. "While there have been no cases of H7N9 in the United States, CDC is following this situation closely and coordinating with domestic and international partners," a CDC spokesperson told The Verge.

Researchers in Japan and the US have analyzed the genes of a new strain of avian (bird) flu that's killed at least 17 people in China in recent weeks, and discovered that some of the new H7N9 viruses have mutated to be more effective and deadlier in humans than they are in birds. The findings "raise concerns regarding their [the virsues'] pandemic potential," according to the researchers, who published their findings in a paper in the journal Eurosurveillance last week.