American parents have been caught selling chickenpox-infected lollipops to other families who want their children to catch the virus while they are young.
Prosecutors in Tennessee have been forced to issue a warning that sending viruses or diseases by post is illegal, after parcels of the infectious sweets were discovered on sale over the internet.
Wendy Werkit, of Nashville, offered to send other parents a "fresh batch of pox" on lollipops or cotton-buds in return for $50 (£31) via PayPal.
Mrs Werkit told a local television station that she had been inspired to sell the products because parents were frustrated that "they can't get it the normal way any more".
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Her advertisement was placed on a Facebook page intended to help parents find a "pox party" in their local area, where children can mix and pick up the virus, which can be more dangerous if suffered later.
Advice for the best way to send chickenpox emerged in a thread of postings on the site. "Tuck it inside a ziplock baggie then put it in the envelope," it said. "Don't put anything identifying it as pox."
Jerry Martin, the US attorney for the Middle District of Tennessee, condemned the practice and said that it was a federal crime to send diseases or viruses across state lines.
"If you are engaged in this type of behaviour, you're not only potentially exposing innocent people to dangerous viruses and illnesses and diseases, you're also exposing yourself potentially to federal criminal prosecution," he said.
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