US President Barack Obama has declared an official disaster in the state of Louisiana in the deep south after wide-spread flooding around Baton Rouge killed at least five people and inundated "thousands" of homes, according to the state's governor.

All that water came down at a time when the US is worried about the arrival of the Zika virus, the mosquito-born disease that has caused thousands of cases of the birth defect microcephaly, or abnormally small skulls and brains in infants.  The insect that carries the virus and other disease - the Aedes aegypti - breeds in standing water, and now there's a lot of it.  Strong flood water often washes away mosquito eggs, but undisturbed pools are the perfect nurseries for the blood suckers.

"We could be seeing an increase number of Aedes aegypti now in the coming weeks," said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston.  "This is crunch time."

Southern US States, counties, and towns have been largely left on their own to deal with the buzzing menace.  President Obama in February asked congress to approve an emergency bill to appropriate US$1.9 Billion for mosquito abatement, Zika vaccine trials, and studies to learn more about how the virus affects unborn babies.  But the opposition Republican-controlled congress has refused to act on a clean bill, or have attempted to poison the bill by putting unpalatable and unrelated budget cuts in that Democrats wouldn't approve.  Even if congress acts, that potential six-month head-start on fighting Zika is gone forever, thanks to the Republican-controlled congress.