Infectious diseases are spreading faster than ever before, the World Health Organization annual report says
With about 2.1 billion airline passengers flying each year, there is a high risk of another major epidemic such as Aids, Sars or Ebola fever.
The WHO urges increased efforts to combat disease outbreaks, and sharing of virus data to help develop vaccines.
Without this, it says, there could be devastating impacts on the global economy and international security.
In the report, A Safer Future, the WHO says new diseases are emerging at the "historically unprecedented" rate of one per year.
Since the 1970s, 39 new diseases have developed, and in the last five years alone, the WHO has identified more than 1,100 epidemics including cholera, polio and bird flu.
"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 says.
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Infectious diseases spreading faster than ever: U.N.