B737-900
Flight Crew Air Transport Pilot (ATP)
Workload; Troubleshooting; Physiological - Other
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Illness / Injury
Flight Crew Took Evasive Action; General Physical Injury / Incapacitation
Human Factors; Aircraft
About an hour into the flight; during cruise at FL350; the A Flight Attendant (FA) called from the aft galley and informed us that all four of the FA's felt dizzy and nauseous as they worked or passed through rows 19 to 22.  They said they did not smell any type of odor.  At that time they informed us that they were feeling better and that they could continue on to our destination.  I then called [maintenance] via Satcom and discussed the issue with them.  We both agreed that since the FA's were feeling better that we would continue on. We also asked the FA's to walk through the cabin and check on the passengers; especially the ones seated between rows 19-22.  They responded a short time later and said everybody was doing well.About 30 minute from Top of Descent (TOD); the A FA notified us that there was a female passenger; 26 years of age; in seat 12F that had the same symptoms as the FA's.  She was put on O2 and we notified [medical services].  [Medical services] advised us to continue on to destination since we were only a few minutes from TOD.  The approach and landing were uneventful.  Upon arrival at destination the paramedics boarded the plane. The passenger in 12F walked off the aircraft without further assistance. The FA's had their blood pressure and pulse checked. The A FA needed to be replaced due to her condition.  Have since learned she deadheaded home and was admitted to the hospital with carbon monoxide poisoning. It looks as though this is an air quality issue.
[Report narrative contained no additional information.]
A B737-900 Crew reported four flight attendants were nauseous and dizzy at cruise. Sometime later all were well but during descent a passenger developed the symptoms then departed unassisted. Paramedics examined the flight attendants: one was removed; deadheaded home and admitted to a hospital for carbon monoxide poisoning.