GENEVA Infectious diseases are emerging more quickly and spreading faster around the globe than ever and becoming increasingly difficult to treat, the World Health Organization (WHO) said on Thursday.
With billions of people moving around the planet every year, the U.N. agency said in its annual World Health Report: "An outbreak or epidemic in one part of the world is only a few hours away from becoming an imminent threat somewhere else."
WHO director-general Margaret Chan said mass travel could facilitate the rapid spread of infectious diseases.
"No country can shield itself from invasion by a pathogen incubating in an airline passenger or an insect hiding in a cargo hold," Chan told reporters.
The U.N. agency warned that there was a good possibility of another major scourge like AIDS, SARS or Ebola fever with the potential of killing millions appearing in the coming years.
"Infectious diseases are now spreading geographically much faster than at any time in history," the WHO said.
It said it was vital to keep watch for new threats like the emergence in 2003 of SARS, or Severe Acute Respiratory Syndrome, which spread from China to 30 countries and killed 800 people.
"It would be extremely naive and complacent to assume that there will not be another disease like AIDS, another Ebola, or another SARS, sooner or later," the report warned.
Since the 1970s, the WHO said, new threats have been identified at an "unprecedented rate" of one or more every year, meaning that nearly 40 diseases exist today which were unknown just over a generation ago.
Over the last five years alone, WHO experts had verified more than 1,100 epidemics of different diseases.
It was therefore vital for countries to share information on outbreaks so risks can be assessed and mitigated, Chan said.
The report called for renewed efforts to monitor, prevent and control epidemic-prone illnesses such as cholera, yellow fever and meningococcal diseases.
International assistance may be required to help health workers in poorer countries identify and contain outbreaks of emerging viral diseases such as Ebola and Marburg hemorrhagic fever, the WHO said.
It warned global efforts to control infectious diseases had been "seriously jeopardized" by widespread drug resistance, a consequence of poor medical treatment and misuse of antibiotics.
This is a particular problem with tuberculosis. Extensively drug-resistant (XDR-TB) strains of the contagious respiratory ailment have emerged worldwide.
Although the H5N1 bird flu virus has not mutated into a form that passes easily between humans, as many scientists had feared, the next influenza pandemic was "likely to be of an avian variety" and could affect some 1.5 billion people.
Chan noted that the last influenza pandemic was in 1968 and had killed about 1 million people. "We have learned from previous pandemics that even the mildest pandemic causes too many premature deaths. We don't want to see that," she said.
She urged countries affected by human cases of bird flu, including Indonesia, to continue sharing virus samples, deemed crucial to tracking the virus and to developing a pandemic vaccine.
(Additional reporting by Stephanie Nebehay in Geneva)