Apr 11, 2013 (CIDRAP News) – New reports of H7N9 avian influenza cases from eastern China continued at a steady pace today, with five more infections and one death confirmed by officials in Shanghai and Jiangsu province.
Rising numbers of human infections and reports in China's market poultry also prompted comments and observations today from two of the world's leading human and animal health organizations.
The new cases boost the total so far from the new virus to 38 illnesses, including 10 deaths. Dates of illness onset from the most recently confirmed cases range from Mar 31 to Apr 4.
Among three cases from Shanghai are a 74-year-old man who died today from his illness, a 68-year-old man who is in stable condition, and an 83-year-old woman who is also in stable condition. Patients from neighboring Jiangsu province include a 31-year-old man who is in critical condition and a 56-year-old man who is also in critical condition.
The younger man works as a chef, according to a report today from Xinhua, China's state news agency. Some of the previously reported patients had been exposed to poultry or poultry environment exposure for the patients, but today's official reports did not mention exposure history for the newest five cases.
In an update today on cases that China reported both yesterday and today, the World Health Organization (WHO) said health authorities are monitoring 760 close contacts, and so far no evidence of ongoing human-to-human transmission has been detected.
Of the 28 patients who have survived their infections so far, 19 illnesses were severe and 9 were mild, the WHO said. It noted that because some relatively mild cases have been reported, it's possible that other such cases haven't been identified and reported. Influenza experts have said serology tests are needed for the new virus to reveal the true clinical profile of H7N9 infections.
A 4-year-old boy from Shanghai who had a mild form of the illness—the only pediatric H7N9 case that has been confirmed so far—was discharged from the hospital yesterday after tests showed he no longer had the virus, according to the Xinhua report.
European experts share observations, concerns
Two top officials from the European Centre for Disease Prevention and Control (ECDC) today weighed in with their early observations on the new virus in a perspective piece in the latest issue of Eurosurveillance. They are Angus Nicoll, MB, CBE, who leads the ECDC Influenza and Other Respiratory Viruses Programme, and Dr Niklas Danielsson, a senior expert in the ECDC's Epidemic Intelligence Section.
They praised China's speed and transparency in detecting the cases, reporting them to the WHO, and depositing genetic information from human and animal H7N9 samples into publicly accessible databases.
The growing number of illness-onset dates more recent than late March could reflect increased awareness among clinicians, the two wrote, but close monitoring is needed to identify any changes in transmission patterns, especially human-to-human spread or infections that surface in other Chinese provinces.
Striking features about the pattern so far is that human cases have been sporadic and that very few possible clusters have been detected, Nicoll and Danielsson wrote. Though the virus has genetic markers associated with improved replication in mammals, there is no clear sign of sustained human-to-human transmission, they wrote.
H7N9 appears to be more transmissible between animals and humans than does the H5N1 virus, they said, pointing out that from January 2010 to March 2013 only seven human H5N1 were reported in China, of which five were fatal.
Several questions remain about the extent and distribution of the virus in China and possibly other countries, but the two experts predicted that surveillance will be a challenge, not only because the low pathogenicity virus (as measured in birds) is difficult to detect but also because of the complex mix of informal and formal poultry sectors that exists in many areas.
For now, the risk to Europe is uncertain, they wrote, but it's important to consider the virologic and sequence analysis alongside the epidemiologic picture. Although early assessment have raised concerns about some of the genetic markers, it's not inevitable that the virus will gain the ability to spread between humans or become a threat to Europe—though both scenarios should be kept in mind, they added.
They pointed out that despite many H5N1 detections in wild birds and European poultry flocks since 1996 when the virus emerged in China, high levels of biosecurity in European Union countries have prevented it from becoming established in domestic poultry.
The ECDC and its global health partners are working quickly to ensure that all national influenza centers in Europe can test for H7N9 as soon as possible, according to Nicoll and Danielsson.
Travelers returning to Europe from China who become ill with severe respiratory infections within 10 days should be evaluated and tested for the new virus, they advised.
OIE: H7N9 an 'exceptional situation'
Officials from one of the world's leading animal health organizations also addressed the H7N9 developments today. Bernard Vallat, DVM, director general of the World Organization for Animal Health (OIE), said poultry suspected of being the source of the human cases don't show any visible signs of disease, making the virus difficult to detect in flocks.
"Based on the information currently available, we are facing a rather exceptional situation," he said in a statement.
The OIE said limited use of a vaccine would be a useful tool for battling the virus in poultry, but one for the H7N9 strain hasn't been developed yet.
"It is important to emphasize that it may be some time before an effective vaccine to protect against influenza A (H7N9) can be made available in sufficient quantities," the OIE said in the statement, adding that if one were available, the agency would be willing to manage regional vaccine banks, as it has done for H5N1 vaccines.
So far the OIE has received reports of eight H7N9 outbreaks in market pigeons and chickens, all in Shanghai and neighboring provinces.
In an accompanying frequently-asked-questions (FAQ) document, the OIE said so far H7N9 has not been found in wild birds in China.
Apr 11 WHO update
Apr 11 Xinhua story
Apr 11 Eurosurveill editorial
Apr 11 OIE statement
Apr 11 OIE FAQ
Apr 11 Hong Kong Center for Health Protection update