Dec. 28 (Bloomberg) -- Bird flu killed three members of a family in Egypt, pushing the number of fatalities worldwide this year to 79, more than reported in the previous three years combined.

The Egyptian Ministry of Health and Population confirmed that the H5N1 strain of avian influenza had infected the three, who belong to an extended family in Gharbiyah province, 80 kilometers (50 miles), northwest of the capital, Cairo, the World Health Organization said in a statement yesterday.

``While being transferred and cared for at the country's designated avian influenza hospital, a 30-year-old female, a 15- year-old girl and a 26-year-old male died,'' the United Nations health agency said in the statement on its Web site. The most recent death occurred yesterday, the agency said.

The patients had all been in contact with sick ducks, WHO said. Egypt has struggled to control H5N1 outbreaks in poultry, first reported in February, leading to at least 18 human cases, including 10 deaths.

Diseased birds increase the opportunities for human infection and provide chances for H5N1 to mutate into a form more dangerous to people. Millions could die if H5N1 becomes easily transmissible between people, sparking a lethal pandemic.

Human Cases in Decline?

The H5N1 virus is known to have infected 261 people in 10 countries in the past three years, killing 157 of them, WHO said yesterday. Last year, 42 fatalities were confirmed, after 32 in 2004 and four in 2003. Six of every 10 reported cases have been fatal and a majority of cases has occurred among children and young adults.

Since July, 26 human cases have been reported in four countries, compared with 88 infections in eight countries in the first half of the year.

``In the second half of 2006, there was a steep decline in the number of case reports, although similar declines occurred in 2004 and 2005, but were then followed by resurgences,'' the influenza team at the European Centre for Disease Surveillance and Control in Stockholm wrote in a Dec. 21 report in Eurosurveillance Weekly.

A few slow months in cases doesn't mean that the threat of pandemic is at an end, said Peter Sandman, a risk communication specialist in Princeton, New Jersey.

``When you install a smoke alarm in your house and then go a year without a fire, that doesn't mean you were foolish to install a smoke alarm,'' said Sandman, who consults to the U.S. Department of Health and Human Services on pandemic communication. ``It means it's time to change the batteries.''

Infection Frequency

Analyzing the frequency of infections over the short term ``is like trying to look at the stars under a microscope,'' said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy in Minneapolis.

Infectious disease is linked to factors including aspects of the environment, such as temperature and humidity, or the length of light in a day, Osterholm said in a Dec. 21 interview.

``Any changes in those can by themselves have an impact, and we see lots of normal variation in diseases as a result,'' he said. ``The question is how do you distinguish long-term changes from what we might consider chance variation. That's what's happening with influenza.''

The virus can now be found in both domestic and migratory bird populations in Asia, even in areas where there have been no large outbreaks, Osterholm said. That may result in opportunities for humans to become infected, and in greater chances for a mutation-driven change, he said.

Vietnam Outbreaks

Vietnam detected a bird flu outbreak that killed 450 ducks in Long My district in Hau Giang province, the third province to report infections this month, the Ministry of Agriculture and Rural Development's department for animal health said in a report posted on its Web site today.

The country reported its first outbreaks since December 2005 earlier this month in Bac Lieu and Ca Mau provinces. More than 12,000 birds have been killed or culled in the three provinces. The country hasn't reported any human cases this year.

``One thing which is very good is that all the ducks in the farm next to the outbreak have been vaccinated, and so they were not infected at all,'' said Bui Quang Anh, director of the animal health department, in an interview. ``It can prove to farmers that the vaccine has worked very well and that they should definitely have their poultry vaccinated.''

Women Over-represented

Females are over-represented among H5N1 patients aged 10-29 years, possibly because it is usually young people and women who look after domestic poultry, the ECDC's influenza team said in Eurosurveillance.

``Human-to-human transmission, as indicated by cluster size, is still extremely inefficient, as it was a decade ago when the first human-to-human transmission took place in Hong Kong,'' the researchers said.

Indonesia, with 74 human H5N1 cases to date, including 57 fatalities, is the country worst affected by the virus. Outside Asia, Egypt has the most cases.

``There is evidence that H5N1 viruses have now become entrenched in backyard poultry in Indonesia, and perhaps also Egypt,'' the report in Eurosurveillance said.

Specimens from the most recent three Egyptian cases tested positive for avian influenza A (H5N1) virus by the country's Central Public Health Laboratory. The virus was also detected in specimens from two of the three patients by the U.S. Naval Medical Research Unit No.3 (NAMRU-3), WHO said.

The samples will be sent to a laboratory that works with WHO for further testing including characterization of the virus, the Geneva-based agency said.

The Egyptian Ministry of Health and Population is further investigating the bird flu cases and has implemented measures to protect public health, WHO said in its statement. The other family members remain healthy and have been placed under close observation, the agency said.

To contact the reporters on this story: Jason Gale in Singapore at j.gale@bloomberg.net; John Lauerman in Boston at jlauerman@bloomberg.net.

Last Updated: December 28, 2006 07:05 EST