China's Second H7N9 Wave Tops Infections Seen In Spring Outbreak
January 31, 2014

China’s Second H7N9 Wave Tops Infections Seen In Spring Outbreak

Lawrence LeBlond for - Your Universe Online

In the past three days the World Health Organization (WHO) has been notified of at least 27 additional laboratory-confirmed cases of human infection with H7N9 avian influenza. According to CIDRAP’s Lisa Schnirring, this second wave of H7N9 infections has surpassed the spring outbreak.

Since the beginning of the New Year a total of 120 lab-confirmed cases have been etched into the books, with 137 cases confirmed since the second wave began, putting that number at one over the spring wave of 136. The total number of deaths associated with both outbreaks stands at 60, according to CIDRAP.

As well, the second wave of H7N9 infections has come at a much faster pace. The first wave of illnesses saw 136 cases over 158 days. This second wave is in its 105th day, with more than 90 percent of cases seen since the beginning of the New Year.

The latest H7N9 case was confirmed in a 75-year-old woman from Nanjing, Jiangsu Province, according to a Xinhua news report. The patient is currently in critical condition.

While the number of new cases has been on a rapid incline, Li Lanjuan, a researcher with the Chinese Academy of Engineering and a specialist in H7N9 prevention, told Xinhua that there has so far been no sustained cases of human-to-human transmission.

Also, Li said her team has identified some mutation in the H7N9 virus this year, but not on a large scale.

"Inter-human transmission is very unlikely," said Li, adding that the virus has not evolved to be extensively drug resistant.

Chinese health officials are expecting flu numbers to begin dropping as live poultry trading has been halted in several cities -- Hangzhou, Ningbo and Jinhua – where the outbreak has been most prominent. As well, the National Health and Family Planning Commission (NHFPC) urged any live poultry markets should be closed if a case of H7N9 is detected.

However, China’s agriculture ministry downplayed the role of poultry in spreading the disease based on surveillance results, which has raised some questions about whether the techniques employed by the ministry are best for measuring infection levels in birds.

The ministry maintains there is no proof of direct H7N9 transmission from poultry to humans and Zhang Zhongqui, the ministry’s director, said only eight of 33,000 samples tested positive for the virus, according to CIDRAP.

A US expert has questioned the validity of China’s testing methods, noting that they could be easily missing H7N9 in poultry.

Dave Halvorson, DVM, an avian expert at the University of Minnesota, St. Paul, told CIDRAP that the surveillance methods – polymerase chain reaction and viral isolation testing – being employed by China’s agriculture ministry is of 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," said Halvorson. "I call this type of surveillance '‘looking for negatives,' because the probability of finding virus in healthy birds is so low."

Halvorson said that since low-pathogenic viruses typically do not make poultry sick, a more effective method for testing them is by active serologic monitoring.

Hong Kong reached an agreement with mainland officials on Jan 16 to incorporate H7 serologic testing in poultry and monitoring began on Jan 24. The government said the method will add another level of surveillance to the already tight systems that are in place to prevent the introduction of H7N9 to Hong Kong poultry.

Despite Hong Kong’s tight security on H7N9 prevention, recent studies have shown detectable levels in live poultry imported from the mainland to Hong Kong SAR, which shows potential for the virus to spread through live poultry there, according to the WHO. Still, the agency maintains there is no indication that international spread of H7N9 has occurred through humans or animals.

However, sporadic human cases are expected to continue in affected areas, with perhaps some spillover into neighboring communities, especially with the increase in trade and transport of poultry associated with the Chinese Lunar New Year festivities, noted the WHO.

The WHO currently does not advise special screening at points of entry with regard to H7N9, nor does it recommend any travel or trade restrictions at this time. It does encourage all countries to continue strengthening influenza surveillance and to continue national health preparedness actions where necessary.