Pushing the number of cases in the second H7N9 influenza wave higher than the first, China reported six more cases today, as well as two more deaths, one of which involved a previously confirmed case.
Today’s new cases lift the number reported in the second wave to 137, topping the 136 cases reported during the first wave last spring.
The country’s agriculture ministry also downplayed the role of poultry in spreading the disease based on its surveillance results, raising questions about whether the techniques used are the best for gauging infection levels in flocks.
A US expert, however, questioned the testing methods Chinese officials are using, saying they could easily miss H7N9 in poultry.
Six cases from three provinces
The six new H7N9 infections are all in adults from three provinces that have reported several cases already.
According to provincial ministry statements translated and posted by the Avian Flu Diary (AFD) blog, they include four from Zhejiang province: a 75-year-woman who is in critical condition, a 76-year-old man who is in severe condition, a 78-year-old man who is in critical condition, and 64-year-old man who is in critical condition.
Guangdong province reported one new case-patient, a 67-year-old woman who died on Jan 28 from her illness, and it reported the death of a previously announced case, according to the AFD report.
In addition, Jiangsu province announced that tests detected the virus in a 75-year-old woman who is hospitalized in critical condition.
China’s latest H7N9 cases boost the outbreak total to 273, according to a case list compiled by the FluTrackers infectious disease message board.
Also, cases in the second wave are piling up faster than during the first wave. The first wave reached 136 cases in 158 days, according to a CIDRAP analysis of illness-onset dates.
But it took the second wave, which began in early October, to reach the same number of cases in only 105 days. And the pace in the past few weeks has been especially brisk.
The two new deaths reported today raise the outbreak’s unofficial fatality count to 60.
In related developments, the World Health Organization (WHO) provided details on 15 case reports from China that it received yesterday. Ten involve women and five involve men. All patients are adults, with ages ranging from 31 to 81.
Nine of the cases are from Zhejiang province, four are from Guangdong, and single cases were reported from Jiangsu province and Shanghai. Thirteen of the patients are hospitalized in critical or serious condition.
All but one of the patients had been exposed to live poultry or a market environment before getting sick. Five of the patients are farmers, and one works as a cook.
Questions raised about China’s poultry surveillance
Despite the reports that many patients in both waves of the outbreak were exposed to poultry or their environments, China’s agriculture ministry today downplayed the connection between poultry and human illnesses.
An official from China’s agriculture ministry said that so far there is no proof of direct H7N9 transmission from poultry to humans, according to a report from CCTV News, the English language news channel of China Central Television, based in Beijing. Zhang Zhongqiu, the ministry’s bureau director, said so far this year only 8 of 33,000 samples were positive for the virus, and all were from live-poultry markets.
A similar pattern was seen during poultry testing last spring in the wake of the first wave of human infections, a puzzling aspect of the outbreak, especially when human H7N9 illnesses in disease hot spots dropped soon after poultry markets were shuttered.
Dave Halvorson, DVM, an avian health expert at the University of Minnesota in St. Paul, told CIDRAP News that media reports describing China’s poultry testing techniques raise questions about their effectiveness.
He said a ProMED Mail post on a recent report from China’s agriculture ministry to the World Organization for Animal Health (OIE) suggests that Chinese scientists are using polymerase chain reaction and viral isolation testing to monitor poultry. ProMED Mail is the Internet reporting service of the International Society for Infectious Diseases.
He said the surveillance method they are using has little value, because the low-pathogenic virus causes few if any signs in poultry. "It's akin to looking for human influenza virus by sampling clinically healthy people—you won't find much virus."
"I call this type of surveillance '‘looking for negatives,' because the probability of finding virus in healthy birds is so low," Halvorson said.
Because low-pathogenic viruses don’t typically make poultry sick, the most effective method is active serologic monitoring, he said. In contrast, passive surveillance for highly pathogenic avian influenza viruses is highly effective, because of severe illness in affected poultry.
On Jan 16, Hong Kong's government announced that it had reached an agreement with mainland officials on an H7 serology testing program for mainland farms that supply poultry to Hong Kong. The program began on Jan 24 and will also apply to local poultry farms in Hong Kong, according to a government statement. It said tests add another surveillance measure to the already tight systems in place to prevent the introduction of H7N9 to Hong Kong flocks.
Hong Kong announced the serology testing program for poultry a few days before other tests found H7N9 in poultry from a certified farm in the mainland’s Guangdong province that had been brought into a Hong Kong wholesale market. The findings triggered the closure of the live-poultry market for 3 weeks and the culling of more than 20,000 birds at the site.
Studies shed light on airway attachment, lab capacity
In H7N9 research developments, an international team based at Erasmus University in the Netherlands compared H7N9 virus airway attachment in different animal models and humans and found that the pattern in macaques, mice, and to some extent pigs and guinea pigs resembles that in humans. The team published its findings yesterday online in the Journal of Virology.
The attachment for those animals was more similar to humans than the pattern they saw in ferrets. They wrote that the findings shed more light on different animal models for influenza.
Meanwhile, a review of the capacity of European labs to detect the H7N9 virus found that 27 of 29 countries said that their generic influenza A detection assays will correctly detect the new virus, according to a report in today’s issue of Eurosurveillance.
Overall, 28 of 31 labs in those 27 countries reported having the ability to subtype H7 viruses, with the remaining 3 labs proposing to send their non-subtypeable viruses to a WHO in London
The survey also found that 22 countries have containment facilities that are appropriate for isolating and propagating the H7N9 virus. Those and other findings suggest that the European Reference Laboratory Network for Human Influenza (ERLI-Net) has quickly adopted good capabilities to detect H7N9 viruses.
Jan 30 AFD post
FluTrackers human H7N9 case list
Jan 30 WHO statement
Jan 28 ProMed Mail post
Jan 16 Hong Kong government statement
Jan 29 J Virol abstract
Jan 30 Eurosurveill report