On Saturday and today, eight new human cases of H7N9 avian flu infection have been reported in China, including one in the capital Beijing, bringing the total so far this year to 51 – eleven of them have died.

The eight new cases include one in Shanghai, one in Beijing, two in Jiangsu Province, two in Zhejiang Province, and two in Henan Province, according to the Chinese Center for Disease Control and Prevention (CDC).

The Chinese CDC says that a 7-year-old girl from Shunyi, northeast Beijing, was confirmed with H7N9 bird flu virus infection. The girl, who is in “a stable condition”, has been admitted to Beijing Ditan hospital.

Beijing health authorities say that the girl’s parents, who breed chickens, have no noticeable flu symptoms. They added that the patient had been in close contact only with her parents.

Before this latest H7N9 virus infection in Beijing, there had been reports of confirmed infection in just Shanghai and the neighboring provinces of Zhejiang, Jiangsu and Anhui.

Two new cases were confirmed today. One is a restaurant chef, aged 34, from Weishi county of Kaifeng city. He presented symptoms on April 6th and is now in a critical condition in an ICU (intensive care unit) at a local hospital. The other is a farmer aged 65 from Zhoukou, who was said to have frequent contacts with poultry in the premises where he lived. He received treatment and is now “in a stable condition.

The Henan provincial center of disease control and prevention confirmed that both patients tested positive for the H7N9 bird flu virus.

A 56-year old man, surnamed Gu, was confirmed on Saturday to be infected with H7N9 bird flu. His wife died of the same infection on April 3rd. The National Health and Family Planning Commission reported that they cannot determine whether the man caught the infection from his wife, citing “insufficient evidence”.

The director of the Shanghai Municipal Disease Prevention and Control Center, stressed that despite the growing number of human infections, there is still not enough evidence to determine whether the H7N9 avian flu virus is human-to-human transmissible.

In Zhejiang Province, which is next door to Shanghai, regional authorities confirmed yesterday that two males, aged 38 and 65 years, were infected with the H7N9 bird flu virus strain. Eleven people are known to have become infected in the province so far.

In Jiangsu Province, which borders both Shanghai and Zhejiang Province, two new cases were confirmed yesterday, bringing the total there to 14.

In Anhui Province, which neighbors Jiangsu and Zhejiang provinces (but not Shanghai), authorities confirmed two cases of H7N9 bird flu infection.

Until yesterday, all H7N9 bird flu infections occurred in Shanghai and neighboring provinces in East China. Beijing, which is 664 miles (1069 kilometers) away, is the first case to be reported in northern China.

China administrative PRC
H7N9 first infected in Shanghai in the east coast, then neighboring provinces, and now Beijing in the north

The H7N9 virus has clearly jumped several provinces to reach the capital. Nobody knows how this occurred. The 7-year old Beijing girl may have caught the infection from another human or directly from poultry. As her parents are fine and have no flu-like symptoms and authorities say she was not in contact with anybody else, it is more likely she caught the infection from poultry (her parents breed poultry).

Chinese health authorities need to find out: 1. How the girl became infected. 2. How the person or poultry who/which infected her became infected. This might not be possible to determine.

Of the eleven people who have died so far, all of them in east China:

  • 7 were from Shanghai
  • 2 from Zhejiang Province
  • 1 from Jiangsu Province
  • 1 from Anhui Province

All the people who were in close contact with the 51 patients so far infected have been carefully checked; none of them have exhibited flu-like symptoms, officials say.

The Beijing government said it would close all markets that sell live poultry. All live poultry trading will be forbidden as authorities take measures to try to stop the spread of H7N9 bird flu infections.

The poultry industry has a large number of chickens that are ready to sell but do not yet have buyers. In Shanghai, city processors have deep frozen 600,000 chickens.

The poultry industry is a major source of food for China’s population. China is the second largest producer of chickens after the USA.

H7N9 is a subtype (serotype) of Influenzavirus A (bird flu virus or avian flu virus). There are several subtypes of bird flu influenza viruses. However, only some strains of four subtypes are highly pathogenic in humans, they are:

  • H5N1
  • H7N3
  • H7N7
  • H7N9 – the subtype mentioned in this article
  • H9N2

Influenza A H7 viruses are a group of influenza viruses. H7N9 is a subgroup of the larger H7 group. H7 viruses normally circulate amongst bird populations, with some variants – H7N2, H7N3 and H7N7 – known to occasionally infect humans. No human infections with H7N9 viruses had ever been reported before these 51 cases from China.

What are the signs and symptoms of H7N9 bird flu virus infection? According to WHO (World Health Organization), signs and symptoms include:

With only 51 cases to go by, WHO emphasizes that the information on symptoms is limited.

There is no vaccine for H7N9. According to antigenic and genome sequencing, neuraminidase inhibitors, such as oseltamivir (Tamiflu) and zanamivir (Relenza) may help in treating infected patients. In a communiqué yesterday, WHO wrote:

“To date, there is limited information to determine whether the reported number of cases represents some or all of the cases actually occurring. As some relatively mild cases of illness have now been reported, it is possible that there are other such cases that have not been identified and reported.”

In March 2013, thousands of dead pigs were found floating in the Huang Pu river, which flows through Shanghai. In a response to speculation among local media and Shanghai residents that the human H7N9 bird flu virus infections might be linked to these pigs, Dr Michael O’Leary, WHO Representative in China on human infection with influenza A(H7N9), said:

“There has been some speculation that there could be a link between the death of thousands of pigs in eastern China, influenza in birds, and the human cases.

However the deaths in pigs in the Huang Pu river may be caused by many factors, and we have not connected the pig deaths to human cases of influenza. Those pigs which have been tested were found negative for influenza viruses. The clinical syndrome in pigs is not compatible with influenza infection.”

Why is H7N9 infecting humans now? – WHO says nobody knows the answer to this question yet. We will not know until we can determine the source of exposure to these human infections. Genetic analyses of these viruses suggest that although they evolved from bird viruses, H7N9 show signs of adaptation to growth in mammals (humans are mammals). “These adaptations include an ability to bind to mammalian cells, and to grow at temperatures close to the normal body temperature of mammals (which is lower than that of birds).”

After several weeks of intense investigation, these new cases of bird flu infections are still baffling experts.

Written by Christian Nordqvist