Sunday, 7 April 2013

First deaths of new bird flu suggest extremely virulent strain


Last week a handful of people were admitted to hospitals in Shanghai suffering from a virus that may have originated in the Yangtze River delta province of Zhejiang in eastern China. They exhibited symptoms consistent with no known human influenza virus. Upon analysing the virus it was discovered to be a strain previously harmless to humans, with the designation influenza A H7N9. The virus has infected 18 people and killed six as of April 6, while four are in critical condition.

A good explanation for influenza is from Foreign Policy magazine, “Influenzas are named according to the specific nature of two proteins found on the virus -- the H stands for hemaggluntinin and the N for neuraminidase. These proteins play various roles in the flu-infection process, including latching onto receptors on the outside of the cells of animals to transmit the virus into their bodies. Those receptors can vary widely from one species to another, which is why most types of influenza viruses spreading now around the world are harmless to human beings.”

According to Chinese officials Beijing is mobilising resources nationwide to fight the new strain of bird flu. Japan and Hong Kong are also increasing vigilance and the United States said it was closely monitoring the situation. However Washington says there is “little” international risk at this time.

Slaughtered birds are bagged at the Huhuai market in Shanghai. - Photo/CFP
The World Health Organisation states in a recent media release that “Any animal influenza virus that develops the ability to infect people is a theoretical risk to cause a pandemic. However, whether the influenza A (H7N9) virus could actually cause a pandemic is unknown. Other animal influenza viruses that have been found to occasionally infect people have not gone on to cause a pandemic.”

Already Chinese authorities plan to cull birds from two live poultry markets in Shanghai and one in Hangzhou after the new bird flu virus was detected at all of the markets. Shanghai officials ordered all live poultry markets to close until further notice. Over 200,000 birds have already been killed as a result of finding strains of the virus on pigeons in the Shanghai area. The fear of outbreak is causing international concern and led to a selling off of airline shares in Europe and Hong Kong.

This particular strain of virus might be connected to a large die-off in pigs and poultry in mid-March. On March 10, a small number of pigs were noticed floating on the Huangpu River, an important source of drinking water for the bustling city of Shanghai. This particular river is a tributary for the mighty Yangtze River, a body of water as important for the Chinese as the Nile is for the Egyptians or the Rheine for the Germans.

By that evening over 15,000 bloated pig carcasses were counted in the river. Those pigs were dumped in the river by upriver farmers after they had died of an unknown illness. It has been assumed that the high level of pollution in both the rivers and air in this part of China caused the deaths. However this explanation fails to offer insight into why thousands of other pigs were spotted in another tributary a few hundred kilometres west of the previous location on the shores of Changsha's primary river, the Xiang. Nor does it explain why thousands of dead swans and ducks were among that particular group of pig carcasses.

In Nanjing, residents photographed dozens of dead sparrows found on Friday, which very quickly circulated online. While another pile of dead birds was discovered in the Sichuan province, hundreds of kilometres away near Lake Qinghai. This area was isolated a number of years ago as the initial mutation point for a fresh strain of H5N1 avian flu which allowed the strain to travel internationally for the first time on migrating birds. At the beginning of April it is unknown how many pigs and birds have been killed by the new avian flu strain, but the discovered carcasses alone number into the hundreds of thousands.

While some have suggested a connection between the pig, bird, and human deaths, Chinese authorities do not agree. The official explanation suggests a sudden change in temperature killed the birds, and the high level of pollution in the area is responsible for the pig deaths. Tests conducted on a handful of the dead pigs returned results not for H7N9, but for Porcine circovirus Type 2 (PCV-2), which is harmless to humans. However, this virus is fatal for only new-born or pig foetuses, whereas the deaths were all of adult pigs. Neither does this reasoning explain the bird deaths nor why many of those birds were found floating in tied plastic bags.

Technicians deal with test reagents for H7N9 bird flu virus April 3, 2013 - ChinaFotoPress
Before the March pig and bird deaths, a handful of cases of human deaths resulting from severe respiratory illness were admitted to hospitals in China. Some of these cases have been killed by the afflicting virus while others are being treated but remain in serious conditions. Other than the fact each have contracted the same H7N9 virus, there is little to connect them. 

The first reported death according to Reuters, was of an 87 year old male on March 4. And because none of the man’s contacts appear to be stricken ill, the virus does not yet seem to be contagious from human-to-human contact. There also does not appear to be any age differentiation at this point among infected human cases. The infected ages range between 27 and 87 years old, with the virus affecting both males and females.

But if 18 people are infected and 6 have died as a result of this strain then its virulence is very high and Chinese authorities will need to draw sound conclusions soon. A virus that kills more than half of people it infects is an incredibly deadly strain and should be treated with the utmost seriousness. The H7N9 strain has already shown it can mutate rapidly to infect new species and there is every possibility it could mutate to be passed from human to human, although presently it cannot.

Complicating matters, a story running in The Guardian claims this particular strain of influenza does not appear to make infected birds visibly sick, making it more difficult to detect and therefore combat.

Currently there is no known vaccine for the H7N9 avian flu strain. But according to CIDRAP News, antigenic and genome sequencing suggests that H7N9 is sensitive to neuraminidase inhibitors. Although the H7N9 strain was known to exist in birds, the flu has never previously managed to infect humans, or any mammals. Finding six people killed and 18 barely surviving due to H7N9 infection is focusing the attention of disease control experts from around the world. It is very likely this virus underwent a mutation making it contractible to mammals, as other strains have done in the past.

And because humans and pigs share extremely similar cell structure, once the virus had attached to pig cells it would not be a difficult step for the virus to infect humans. It is unknown at this time whether the deaths from the pigs, birds, and humans all arise from the H7N9 strain, but more research needs to be undertaken. This virus is killing or critically injuring a majority of infected human cases, making the virus especially dangerous.

Chinese authorities say Shanghai has sufficient disease prevention supplies and is prepared for an outbreak. They assure people not to worry and to avoid the panic-buying of goods. But just what kind of virus they will be dealing with, or how widespread and virulent it actually is, so far remains disturbingly unknown.

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