A third of the world could potentially become infected with the new influenza A(H1N1) virus, dpa cited a senior World Health Organization (WHO) official as saying today. "Looking at past pandemics, a third of the world's population could be infected," Keiji Fukuda, the WHO's head of health security, said. That would roughly be equal to 2 billion people. So far, the United Nations health agency reported the number of laboratory-confirmed cases of infections of the new influenza A(H1N1) virus stood at 2,099 in 23 countries, with a death toll of 44. The rising number mostly reflected confirmed cases of the virus that was dubbed swine flu after it was first detected in Mexico late last month. Fukuda could not estimate how many people would become seriously ill or die from an infection of the new virus, saying the WHO was still trying to understand the nature of H1N1. "Our spectrum of understanding of the virus is evolving," he told reporters in Geneva. WHO officials have said research was under way to create a vaccine for H1N1 and expected manufacturers could role one out within four to six months. The number of doses that could be produced in the first year would likely be just above 1 billion. The WHO has maintained its pandemic influenza alert at phase 5, meaning human-to-human transmission at the community level was detected in two countries in one region, in this case North America. Fukuda said he was not aware of any plans to raise the level to the highest, phase 6. The WHO confirmed that Mexico had 42 deaths related to the disease. The United States, which reported two deaths, was the only other country to report fatalities. Mexico had 1,112 laboratory-confirmed cases, while the US had 642 such infections and Canada reported 201 instances, the WHO said. In Europe, Spain remained hardest hit with 73 cases and Britain had 28 infections. Germany reported nine cases. New Zealand had five cases and South Korea two.