How Risky is Bird Flu Virus H7N9 and Future Strains?

A new type of bird flu has developed in China, known as H7N9. WHO (The World Health Organization) has warned that this bird flu is an "unusually dangerous virus". These virus infections usually occur when the virus infections humans after contact with chickens and other infected bird.

It is too early to know whether this strain of bird flu poses a major threat threat to human health in Asian and the rest of the World. The key factor affecting the threat is whether the virus develops the ability for human to human transmission.

So far about 20% of people have died. The infection causes severe pneumonia in the worst cases, organ failure and blood poisoning. So most cases have been linked to infections via contact with poultry.

However, if the virus mutates or gets the ability to rapidly spread human-to-human it will be a much more severe threat threat. Scientists have warned that the virus is rapidly mutating. A previous major bird flu, called H5N1, killed more than 300 people 1997 but did not develop the ability to just between humans.

A study published in the Lancet has reported that H7N9 influenza maybe blend of four viruses, perhaps more, with origins in chickens and ducks. It may have remained unreported for some time and the symptoms tor mild flu cases are similar to the common flu.

Unlike the previous bird flu H5N1 outbreak, the latest virus is not deadly to poultry. This makes it is much harder to identify reservoirs of infected birds and to track the spread of the virus in ducks, chickens and other birds such as pigeons.

Early research suggests that there is virtually no immunity and that the virus has not infected many humans before.


This article provides general questions and answers about the new bird flu virus and the risk it poses.

 electron micrograph (magnification 108,000x) of of two avian influenza A (H5N1) viruses
electron micrograph (magnification 108,000x) of of two avian influenza A (H5N1) viruses | Source
Infects the Lungs first causing pneumonia and possible organ failure and death
Infects the Lungs first causing pneumonia and possible organ failure and death | Source
How bird flus pose a threat to humans
How bird flus pose a threat to humans | Source
How mutations and combinations and genetic material can lead to the ability for human-to-human transmission
How mutations and combinations and genetic material can lead to the ability for human-to-human transmission | Source

History and Background for the New Bird Virus

Towards the middle of April 2013, Chinese authorities has reported that the bird flu had caused about 14 deaths among about one hundred confirmed cases across six provinces in China. Early studies suggest that it is unusual in its ability to cause such severe disease in humans. Chinese authorities are trying to identify the bird populations that are the reservoir of the disease so they can lower human exposure to the virus.

But this task is hard because the virus seems to have low mortality and sickness rates among birds. This makes it harder to identify and eradicate the sources. The cases so far reported spread from over a 1000 km length of coastal China, from Beijing to Shanghai, and cases have been reported in Taiwan. So the opportunity to find and control the source of infection may already be too late.

Authorities are nevertheless trying to find the sources of infection and control them. There is no evidence so far that the virus can be transmitted from human to human. The virus is mutating to different variants and the worry is that it may randomly pick up or develop genes which aid its transmissibility. The other concern is that it may pick up resistance to some of the antivirals, for which there are few options.

How Large is the Risk and Threat?

Various Scientists, WHO and Health authorities have described the new virus as a serious threat that poses a major cause . This situation is being monitored carefully as the number of reported cases has grown alarmingly to over 100 in about a month. The disease appears to cause serious illness with 20% death rates and serve pneumonia in many of those infected. The H7N9 is potentially more dangerous than the previous bird flu virus H5N1.

What symptoms appear in Humans Infected with Bird Flu?

The main symptom is severe pneumonia. In severe cases the virus can completely swamp the immune system, causing a major heath risk known as cytokine storm. This can lead to organ failure, blood poisoning and death, particularly when it appears there is little residual immunity to the H7N9 virus.

Is it a Cause for Concern Now?

While a major threat there is no reason for major concern just yet. The virus has so far only been shown to spread from birds to humans. The virus has been detected in ducks, chickens and pigeons in markets in China. There has been no evidence of it spreading to wild bird populations. The risk of infection is therefore confined to people who have close contact with infected birds in Asia. However, this situation could worsen if the virus mutates or gets genes that allow human-to-human transmission to occur easily. If and when this happens it will trigger major concern throughout the world.

What should People Look out for as Signs that the Situation is Worsening?

The biggest trigger for extra concern is evidence of spread from humans-to-humans. Given the high rate of international air travel, and the incubation time of 5 days or more the virus could quickly spread without much chance of stopping it. There is concern that the mutation rate is high and this may occur. The virus may also spread to wild bird populations and be spread via migration patterns throughout the world.

The other triggers for concern would be a dramatic rise in reported cases and signs of it spreading to other countries. Also if the virus shows signs of infecting other animals, especially pigs, this can hasten its spread and increase the chances of dangerous mutations developing.

Has Bird Flu infections in Humans Occurred Previously?

Viruses jump between species quite regularly, but usually they are not very successful in the secondary host. The last major Bird flu to cause sickness and deaths was the H5N1 virus which, made the jump to humans in 1997 and killed about 300 people. However H5N1 did not develop the capacity for human-to-human transmission. The last deadly world pandemic was the 1918 Spanish flu, which killed about 40 million people world wide. There have been unproven suggestions that this virus responsible - originated in birds. Once again it is a numbers game and there are several hurdle or barriers the virus has to bypass in order to becomes a serious threat worldwide.

What’s the difference between the new Bird Flu Virus H7N9 and the H5N1 Virus?

Although it is early days, it appears that so-far H7N9 is much less deadly than the previous Bird Flu that infected humans, H5N1, which had three-times the mortality rate at 60% compared with 20% for H7N9. But it is early days and the virus could mutate into a more deadly form. This may pose extra risks because H7N9 could spread more easily, carried by people with milder infections. On the flip-side H5N1 killed ducks, chickens and other birds, H7N9 does not. This is important as it increases the risk the virus spreading between flocks of wild and domesticated birds. H7N9 infected flocks will be harder to detect.

© 2013 Dr. John Anderson

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