The pace of new H7N9 avian flu cases in China over the past week is rivaling the daily crush of infections that occurred during the first peak of activity last spring after the virus first emerged, with reports today of seven new illnesses, one of them fatal.
What began as a trickle of reports in October that signaled H7N9's resurgence in humans, primarily from poultry exposure, has expanded over the past few weeks to several cases reported each day. Thirty-one have been confirmed from Jan 10 through today, a number below but approaching the 38 cases reported during the peak week of disease activity, which began on Apr 8, 2013.
Experts contacted by CIDRAP News say the situation bears close monitoring but differed in their level of expressed concern over the situation.
The spike in activity comes as China enters a heavy travel and shopping period for its Spring Festival season, marked by the Lunar New Year celebration on Jan 31. China estimates that its citizens will make about 3.62 billion trips during the 40-day holiday travel rush, according to a report today from Xinhua, China's state news agency.
Against the backdrop in H7N9 activity, Chinese health officials have aired concerns about crowded travel conditions and the chance that people visiting urban areas could carry the virus back to their rural homes.
Today's report: 7 new cases, 1 fatal
Hong Kong's Centre for Health Protection (CHP), citing official mainland sources, said that Guangdong, Fujian, and Zhejian provinces have two new H7N9 cases each, and Guizhou province has one. The patients are all adults, ages 20 to 76, and five are men. The six survivors are hospitalized, four of them in critical condition.
All of the provinces have reported several other cases recently, except for Guizhou, which is reporting its first H7N9 case, in a 38-year-old man got sick while working in Zhejiang province. News of his illness first appeared in media reports on Jan 13 that said he had a suspected infection, but his H7N9 illness has now been confirmed.
Guangdong province's cases involve a 59-year-old man from Guanzhou and a 76-year-old woman from Foshan, according to the CHP. Fujian province's new case-patients are both from the city of Quanzhou, a 30-year-old man, plus a 60-year-old man who had a history of poultry contact.
Meanwhile, Zhejiang province's patients are a 20-year-old woman from Hangzhou and a 58-year-old man from Taizhou, located about 171 miles southeast of the provincial capital.
The new cases push the H7N9 outbreak total to 188 cases and the number of deaths to 53.
Latest WHO confirmations
In related developments, the World Health Organization (WHO) today acknowledged three H7N9 cases initially reported by China on Jan 14, filling in several more clinical details about each of the cases.
Two of the patients have a history of exposure to poultry, including a 58-year-old man from the Zhejiang province city of Hanzghou and a 50-year-old man from the Fujian province's Jinjiang City. Both men are hospitalized in critical condition.
The third patient is a 29-year-old man who is also from Hangzhou who is hospitalized in serious condition.
Experts weigh in on H7N9 momentum
Joseph Bresee, MD, chief of the Epidemiology and Prevention Branch in the US Center for Disease Control and Prevention Influenza Division, said the increasing number of confirmed cases reported from China during the past few weeks bears watching closely.
"Fortunately, despite additional cases, Chinese health officials haven't reported changes in the epidemiology of the virus that would indicate an increased capacity for spread between humans," he said.
Gregory Hartl, a spokesman for the WHO, said the surge in new cases hasn't changed the agency's risk assessment. He said H7N9 is still a virus that causes sporadic human infections and doesn't appear to transmit well from human to human. "We have only seen a handful of human clusters and only very limited human-to-human spread," he said.
Research studies published over the last few months, designed to help gauge pandemic risk the new virus poses, have found H7N9 currently has limited ability for airborne spread.
Hartl said health officials haven't seen H7N9 before in January and February, so they aren't sure what to expect. However, he added that since the months are the peak of flu season and H7N9 is a flu virus, "it would not be surprising—in fact it would be expected—that we see an upsurge in cases."
University of Minnesota infectious disease expert Michael T. Osterholm, PhD, MPH, said the world has almost a year's worth of experience with H7N9 in humans and poultry under its belt, and there is not the same level of "unknowns" as a year ago.
"But I worry that most of the world seems asleep at the switch, " he said, adding that activity over the past 10 days has been as robust of a case onset period as health officials have seen so far. "We're right there. What's different?"
The steady stream of new cases could mean that Chinese health officials are better at detecting cases, but he added that it doesn't look like they missed many cases last year in the early months of the outbreak. "There must be a similar widespread circulation in poultry," said Osterholm, who is the director of the Center for Infectious Disease Research and Policy, publisher of CIDRAP News,
Recent H7N9 developments raise questions about what's being done to minimize the risks to humans and should be setting off bells, whistles, and sirens warning about the threat, he said. "Each one [case] is another throw at the genetic roulette table."
Jan 16 Xinhua report
Jan 16 CHP statement
Jan 16 WHO statement