Authorities in northern Greece say some 70 children living at a camp on the Greek-Former Yugoslav Republic of Macedonian (FYROM) border have received hospital treatment over the past three days, for fever and diarrhea.
Some 14,000 people are camped out near the border town of Idomeni, many in small tents normally used by summer vacationers. Torrential rain has added to the desperate conditions at the site, with tents sinking in mud and soaked firewood making it impossible to start camp fires.
Government health experts at the camp say there is no sign yet of an infectious disease outbreak, but have been urging refugees at Idomeni to move to nearby army-built shelters.
At the nation's main port of Piraeus, near Athens, authorities began transporting hundreds of migrants and refugees to shelters in central Greece to try to ease overcrowding there.
The government says nearly 42,000 people are stranded in Greece following border restrictions and closures by Austria and several Balkan countries that started last month.