In Vietnam the brother of a 47 year old man who died of the bird flu in Hanoi has been confirmed with the H5N1 bird flu virus.

This is alarming news because the brother's only contact with the virus was through his sibling.

He had no contact with chickens and was NOT living near any bird flu outbreaks in poultry.

Although this case is considered highly likely to be human to human transmission of the bird flu virus there is still room for doubt.

A week before the eldest brother fell ill from the bird flu virus the family killed and ate a duck.

Since ducks can carry the bird flu virus without symptoms it is possible (but unlikely) that this was the source of contamination.

In another likely human to human case of the bird flu in 2004 a mother contracted the virus after nursing her sick child in hospital.

The bird flu virus has proved difficult to diagnose - being similar in symptoms to common pneumonia.

With some sick patients testing negative to carrying the virus twice before finally testing positive authorities fear that human cases might be more widespread than was previously suspected.

Scientists have noted that in many clusters of the bird flu virus outbreak human to human infection may be a more logical explanation than concluding relatives who contracted the disease days apart got the virus from the same dying bird.

In one questionable case the Vietnamese government was ridiculed when it suggested that a man developed bird flu symptoms 16 days after eating raw duck blood pudding.

A prominent bird flu specialist from the Hong Kong university suggested it was for more likely the bird flu was passed from human to human - in this case from his infected brother.

Dr Henry Niman, a biochemist in Pittsburgh says health authorities are too conservative and the cases of human to human bird flu transmission are more likely to be around the 20 to 30 mark.

Dr David Nabarro, chief pandemic flu coordinator for the United Nations said that the bird flu is still rated at a level 3 on the pandemic alert system: "No or very limited human to human transmission."

Nabarro said at present any human to human transmission of the bird flu virus is "very inefficient".

Hans Troedsson of the World Health Organization in Vietnam warned the more people who have the bird flu virus the higher the chance it will mutate to a virulent human to human virus with the very real possibility of unleashing a deadly bird flu pandemic.

Troedsson said with the threat of the bird flu mutating to a human to human virus and the deadly consequences if it does it's a "disappointment that the international community is not responding more adequately to the threat."

What is the most practical means of protection from the bird flu?

What can we do every day to lower our chance of catching the bird flu and other respiratory viruses like SARS the common cold and influenza?