In Russia, by contrast, injecting heroin with dirty needles is the main source of infection.
Information available so far points to Farm Rich products as one likely source of infection, the agency said.
"The most important goal remains to locate the source of infection so that measures to minimise contact can be taken", said Prof Ian Jones, Professor of Virology, University of Reading.
Eggs have not been a major source of infection in humans for this particular strain of salmonella, enteritidis, in the last twoor three years, said Patrick McDonough at Cornell University's School of Veterinary Medicine.
Authorities have not determined the source of the infection, said Hong Kong's Chief Executive Donald Tsang.
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In the hunt for the source of the infection, additional testing of farms is planned, said Malik Peiris, a University of Hong Kong microbiologist.
Investigations are taking place to find the source of the infection, and close family of the children have been offered a vaccination as a precaution.
Africa is the only place in which wild monkeys carry SIV - which points the finger at the continent as the source of the infection.
The WHO said investigations were being conducted into the likely source of the infection, the method of exposure, and the possibility of human-to-human transmission of the virus.
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The schools and day care centers were told to close for 14 days as investigators tried to identify the source of the infection, said Tsang, the chief executive.
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However, it warns that two clusters in Saudi Arabia and Jordan, "raise the possibility of limited human-to-human transmission" or they could have been exposed to the same source of the infection.
Tracking down the source of a foodborne infection is notoriously difficult.
"We keep wiping it off, and it keeps coming back, " says a source familiar with the network infection, one of three that told Danger Room about the virus.
At the final stage of the infection, the viruses destroy the cells they have infected, a process that provides a rich source of refractory compounds.
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