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Current H7N9 Wave Rivals Last Spring's Case Total

University of Minnesota Center for Infectious Disease Research and Policy
News & Perspective (UMN)

Lisa SchnirringNews Reporter, CIDRAP News

January 28, 2014

China's steady rise in H7N9 avian flu cases continued over the past 3 days, with 14 new cases from five provinces, as the latest test results in poultry showed a conflicting picture of the virus on farms, including positive samples found today in birds sent to Hong Kong.

The fresh round of infections—coming at a pace matching last year's peak—could soon eclipse last spring's outbreak totals and come as poultry trade and consumption are high in the lead-up to Lunar New Year celebrations later this week.

So far 116 cases have been reported since October 2013, a number that could soon reach or exceed the 136 H7N9 illnesses reported during the outbreak's first wave last spring, a number that includes 2 July cases.

Though the virus doesn't currently appear to spread easily among humans through the airborne route, China's cultural traditions involving live poultry, where the virus spreads silently, put exposed people at risk for zoonotic infections that can quickly progress to severe pneumonia.

Hot spots report more cases, WHO provides more details

Hong Kong's Centre for Health Protection (CHP), in two separate statements, announced initial details for eight new H7N9 illnesses: five reported on Jan 25 and three reported on Jan 26. Five of those patients are from Zhejiang province, two from Jiangsu, and one from Guangdong.

In addition, four provinces reported six new cases today, two from Fujian province, two from Guangdong, one from Hunan, and one from Jiangsu.

According to provincial statements in Chinese translated and posted by Avian Flu Diary, and infectious disease news blog, the patients include three men ages 68, 69, and 72, and three women ages 58, 74, and 77. The 68-year-old man died from his infection, according to the statement from Guangdong province.

The World Health Organization (WHO) fleshed out more details about 19 cases reported over the past 4 days, including the ones reported yesterday, according to separate statements from Jan 25 and today. Patient illness onsets range from Jan 10 through Jan 20. All are adults, ranging in age from 23 to 82. Ten are men and nine are women.

Eleven of the patients are in critical condition, and eight in serious condition. Investigations so far have found that 10 patients had been exposed to poultry and four had been exposed to live-poultry markets.

Over the past few weeks, China has averaged about five to seven new H7N9 cases each day, and the new cases reported over the past 3 days boosts the outbreak total to 252, according to a case list compiled by the FluTrackers infectious disease message board.

Less clear is the number of deaths. Most of the patients reported over the last several weeks were said to be in severe or critical condition and may still be hospitalized. China's Center for Disease Control and Prevention (China CDC) said today that 19 deaths have been reported so far this year among 96 cases reported so far, Xinhua, China's state news agency reported. The unofficial number of deaths is 57.

Shu Yuelong, director of the Chinese National Influenza Center, told Xinhua that the case-fatality rate (CFR) ranges from 20% to 30% and that the risk assessment is unchanged, because so far no H7N9 virus mutations that could affect transmissibility have been found, and so far there is no sign of sustained human-to-human transmission.

An updated risk assessment from the WHO last week said so far the CFR is not as high as the first wave of infections last spring, and that virus samples from the second wave are similar to the first wave, as well as to strains recommended for H7N9 vaccine development.

Mixed signals from H7N9 tests on farms

Meanwhile, China's agriculture ministry said today that tests on farms so far this year have found no H7N9 in poultry, according to a separate report from Xinhua. It said no positives were found among 33,400 samples tested from 2,402 sites.

It added, though, that eight positive samples were found among samples from live-poultry markets in Guangdong, Fujian, Zhejiang, and Guangxi Zhuang autonomous region.

In a report today to the World Organization for Animal Health (OIE), China's agriculture ministry described H7N9 findings at agricultural markets in Guangdong and Fujian provinces. Of 185 chicken specimens collected in Guanzhou in Guangdong, two from different markets were positive, and 1,200 birds were culled to curb the spread of the virus.

In the Fujian province city of Quanzhou, tests on 220 specimens—from chickens, pigeons, ducks, and environments—found only one H7N9-positive result, in an environmental sample.

A similar pattern was seen during agriculture ministry testing after the virus was first detected last spring: no positive samples were found on farms, and only a few were detected in poultry market samples. The results are puzzling, because provincial health ministry reports have said several of the patients infected with the virus were farmers, and official reports say large percentage of H7N9 cases were exposed to poultry or visited live-poultry markets.

Fueling more questions about H7N9 circulation on China's poultry farms, Hong Kong's government today said it detected the virus in a number of samples from a shipment of live chickens that were imported from a registered poultry farm near the Guangdong province city of Foshan, according to a statement posted on the government's Web site.

Hong Kong said it has been testing live poultry imported from the mainland since April 2013, and the findings are the first for H7. In response, the government is closing the agricultural market that received the birds for 21 days and will cull 20,000 poultry that are at the site.

Ko Wing-man, MBBS, secretary for food and health, said in a statement that officers will also inspect Hong Kong poultry to ensure that local birds aren't infected with the virus.

CDC updates H7N9, H5N1 testing recommendations

In other avian developments, the US Centers for Disease Control and Prevention (CDC) has updated its testing recommendations in separate documents for H7N9 and H5N1.

For each virus, the CDC describes testing recommendations based on clinical illness and exposure criteria. For both viruses, CDC recommends testing of severely ill hospitalized patients for whom no other infectious cause has been identified.

The exposure criteria for each virus are customized to reflect the geographic areas where the virus has been found.

CDC's guidance updates are part of a larger effort to modify the information, based on the latest data, and to combine guidance for the two viruses, when appropriate. For example, the agency recently revised its interim recommendations that combine healthcare infection control information for both H7N9 and H5N1.


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