Promising plants can be quickly killed by bacterial wilt. The bacteria live on the mouthparts of cucumber beetles, so it only takes a few beetles to cause significant problems. Once they are infected, plants cannot recover from bacterial wilt.
The best way to prevent this problem is to grow plants beneath floating row covers until they start to bloom and need to be visited by pollinating insects. Cucumber beetles can also be collected with a hand-held vacuum, and you can capture some in yellow pails filled with soapy water. Traps baited with pheromone lures are widely available. There are several resistant varieties, and non-bitter or 'burpless' cucumbers are non-preferred by cucumber beetles, so they are naturally resistant to this disease.
Pull up infected plants and compost them.