Date: 201907
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: A330
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Confusion; Distraction; Physiological - Other; Situational Awareness
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: One hour into flight; at cruise; lead Flight Attendant called to report a dirty socks smell with a resultant headache. He described the odor localized at row 22; AC left. He further stated that one other Flight Attendant was feeling dizzy. He went on to say; that Flight Attendant was well familiar with the odor as he had experienced four previous events. We quickly established sat phone contact with Dispatch and Maintenance. I advised them that I would keep them informed; especially should the situation worsen. Shortly thereafter; the lead Flight Attendant called and said the smell was expanding to cover approximately four rows around row 22; now AC left and right. He further stated that more flight attendants were feeling ill with dizziness; coughing and headache symptoms. At this point; I made the decision; with the help of the lead; First Officer and [Relief Pilot] (he had quickly been summoned back to the flight deck from break) to return to ZZZ. I asked the Flight Attendant to keep me informed. The decision to return to ZZZ was based; in part; that the smell was localized and pax and crew had been moved out of the affected area. Shortly after informing ATC and reversing course; the Lead informed me that the majority of crew were now suffering symptoms and that one was vomiting and on O2. At that point; I made the decision to [advise ATC about a medical event] and land ASAP which was ZZZ1. At that point we were approximately 60NM north of ZZZ1 at 37;000 feet. Through CRM; duties were assigned; and we began our descent. Because we were so close to ZZZ1; the complete QRH procedure was not completed. Without being too rushed; we got the airplane on the ground approx. 25-30 minutes after the decision to [advise ATC]. A smooth overweight landing (413;000 lbs.) was accomplished with the requisite parameters entered in the logbook. After the pax were removed; our flight attendants and [Relief Pilot] were taken to the hospital for evaluation.


Second narrative: [Report narrative contained no additional information.]


Synopsis: A330 flight crew reported executing medical divert due to 'dirty socks' odor in passenger cabin which resulted in the majority of the flight attendants experiencing health issues.