Explained: Why plane passengers are getting sick

Monday's medical emergency at Auckland Airport was just the latest in a series of similar incidents around the world, which all appear to lead back to one specific location.

An alert was raised by the pilot of a Virgin Australia flight from Melbourne to Auckland who reported there were a number of passengers onboard feeling ill.

The incident was almost identical to what happened on an Emirates flight to New York from Dubai. It was isolated at JFK Airport for two hours while authorities checked on the 500 passengers onboard. Ten were subsequently hospitalised with flu-like symptoms.

Just a day later, two flights to Philadelphia landed with numerous passengers also needing treatment due to flu-like symptoms.

So what's causing so much illness?

All of the affected flights had one thing in common: they were carrying passengers on their way home from Mecca in Saudi Arabia, the location of the Hajj, which is currently experiencing a major flu outbreak

The Auckland Regional Public Health Service told Newshub a large number of the passengers on board the Virgin flight had attended the Hajj, which ended on 24 August.

An Emirates plane in quarantine in New York.
An Emirates plane in quarantine in New York. Photo credit: Image - Twitter/@SweeneyABC

World Health Organisation figures show of the 2237 cases of Middle Eastern Respiratory Syndrome (MERS) reported globally, 1861 of those cases were in Saudi Arabia.

Official advice to travellers from New Zealand heading to the Hajj is to make sure all of your vaccinations are up to date, including those against the flu. 

Authorities say potential outbreaks - like the one in Auckland on Monday - are the reason why it's important to have proper procedures and checks in place.

"Most infectious diseases take more time than a long-haul flight to develop. It is always possible that one or more passengers board a plane who are unwell, or who become unwell during the flight," said Dr Shanika Perera, a Medical Officer of Health at the Auckland Regional Public Health Service. 

He said the pilot did the right thing by alerting authorities to the issue onboard.

Authorities surround A380 flight in New York.
Authorities surround A380 flight in New York. Photo credit: Image - AAP

"These passengers could have an illness that poses a potential public health threat to New Zealand, such as MERS," said Dr Perera.

"Precautions may include giving information to passengers in case they develop symptoms, screening for possible illness and on occasion, a full medical assessment. Sometimes this requires the flight to remain on the tarmac with passengers and crew on board while these checks take place."

The Ministry of Health advises anyone who gets sick with a cold or flu-like symptoms within two weeks of returning from Mecca should seek medical attention. They should advise the staff at the health facility they're visiting that they've recently come from Saudi Arabia, as they may need to be kept isolated from other patients. 

All of the passengers from Monday's Virgin flight have been cleared by the Ministry of Health.