Officials in Egypt and Vietnam said bird flu has claimed more victims in their countries, with the Egyptian death the third reported in less than a week.

Egypt's health ministry said a 33-year-old woman, from Kafr el-Sheikh province, died Friday, bringing to 26 the number of Egyptian victims of the H5N1 viral strain.

Officials said a 25-year-old woman and a six-year-old boy, both from Cairo, died earlier in the week.  

Also Friday, Vietnam's health ministry said that a 23-year-old woman from the northern province of Thanh Hoa died Thursday.

Her case was Vietnam's fourth reported H5N1 infection this year.  All of them were fatal.

Vietnam has the second highest number of bird flu fatalities, 65, after Indonesia, where the virus has killed 115 people.  Egypt is the most affected country outside of Asia, with 65 confirmed cases.   

The World Health Organization says more than 250 people have died from the virus worldwide since the first human cases were discovered in 2003.

The virus normally passes from bird to bird and occasionally to humans.  But experts fear a mutation could allow it to spread easily between people and cause a global pandemic.