Skip to main content

Researchers: Elderly more at risk from H7N9

By Peter Shadbolt, CNN
updated 7:13 AM EDT, Tue April 23, 2013
China's health ministry has confirmed 105 cases of H7N9 and 21 deaths from the virus.
China's health ministry has confirmed 105 cases of H7N9 and 21 deaths from the virus.
STORY HIGHLIGHTS
  • Research into the H7N9 virus suggests the risk of contracting serious illness rises with age
  • China's health ministry on Monday confirmed a total of 105 cases and 21 deaths
  • The virus has been identified in Beijing, Shanghai and four provinces including Shandong for the first time
  • The WHO has said so far there is no evidence of human-to-human transmission in H7N9

(CNN) -- Research into the H7N9 virus suggests the risk of contracting serious illness rises with age and that more people may be infected than the 105 cases reported, according to a study by the Hong Kong University.

Benjamin Cowling, associate professor at HKU's public health research center, told CNN that a disparity had emerged in data focusing people's exposure to live poultry.

"Essentially there are more exposures to poultry in older adults than in younger adults, but the difference in exposures is not as big as when we look at the differences in age of the number of serious H7N9 infections," Cowling said.

He said that if age were not a factor in the seriousness of infection, then researchers could expect the pattern of the disease to exactly match the pattern of exposure.

"What we're seeing is that half the serious cases are above 60 years of age," he said. Milder symptoms also meant that many more people may be infected with the virus than is currently known because people potentially infected with H7N9 were not seeking medical attention for what seems like a mild cough or fever.

Read more: Bird flu puts spotlight on age-old traditions in China

Map: Bird flu in China  Map: Bird flu in China
Map: Bird flu in ChinaMap: Bird flu in China
Poultry markets closed over bird flu
New deadly strain of bird flu in China

"One of the reasons that SARS was easier to control was because all of the infections were serious so the patients had to be hospitalized and isolated," he said. "It's easier, then, to reduce onward transmission."

So far, however, there is no evidence of human-to-human transmission in H7N9. Researchers were struggling to discover why an early strain of bird flu -- H5N1 -- attacked a mainly younger demographic of people in their 20s and 30s.

Exactly why influenza strains are more serious in different age groups was still a subject of ongoing investigation, Cowling said.

"It's not completely clear what happened in the 1918 Spanish Flu pandemic," he said. "Certainly the burden of severe illnesses fell disproportionately on younger adults."

He said the normal profile of an influenza epidemic was that the highest proportion of infection is with younger children.

Read more: China's bird flu mystery

"That is a classic feature of influenza viruses but it seems from the mortality curves (of Spanish flu), the highest death rate was in young adults and that suggests something unusual."

World Health Organization officials this week visited Shanghai as part of a week-long visit to China to gauge the response to the outbreak. Keiji Fukuda, assistant director-general for health security and environment of the WHO told a news conference that there was no "sustained" pattern to the H7N9 outbreak that suggested human-to-human contact. Last week, however, a spokesperson from the Chinese Center for Disease Control said that as many 40% of the cases had had no contact with poultry.

China's health ministry on Monday confirmed a total of 105 cases, in Shanghai, the capital Beijing and four provinces including Shandong for the first time. A death on Monday night in Shanghai brought the death toll from the epidemic to 21 people.

ADVERTISEMENT
Part of complete coverage on
updated 8:40 AM EDT, Wed August 20, 2014
The beheading of U.S. journalist James Foley by ISIS militants brings into focus the risks faced by reporters in conflict zones.
updated 8:19 AM EDT, Wed August 20, 2014
In an exclusive CNN interview, Lance Armstrong admits to having a "f**k you" attitude.
updated 4:58 AM EDT, Tue August 19, 2014
Summer isn't over yet. These new hotels are keeping it alive and fresh.
updated 3:40 PM EDT, Tue August 19, 2014
You've seen her turn on the catwalk, but her income might make your head spin.
updated 8:36 PM EDT, Tue August 19, 2014
The pain that Michael Brown's parents are going through is something Sybrina Fulton can relate to. She, too, lost a son in a controversial shooting.
updated 5:04 AM EDT, Tue August 19, 2014
19-year-old Udi Segal explains why he won't join the country's military.
updated 8:34 AM EDT, Tue August 19, 2014
The sights couldn't be sadder: Animals killed or suffering through war in Gaza.
updated 9:14 AM EDT, Mon August 18, 2014
They are the faces of a community on the run. Photographer Warzer Jaff documents the plight of the Yazidis.
updated 7:50 AM EDT, Tue August 19, 2014
A cameraman films a massive New York City subway rat charging at him and attacking him. WPIX reports.
Drinkers guzzled an incredible 10.3 billion liters of this brand in 2013, making it the world's No.1 beer. And you may have never heard of it.
CNN joins the fight to end modern-day slavery by shining a spotlight on its horrors and highlighting success stories.
Browse through images from CNN teams around the world that you don't always see on news reports.
ADVERTISEMENT