How flu is transmitted aboard passenger airliners (Not the way you may think!)

by B. N. Sullivan

Unfortunately, many people are beginning to panic about the present outbreak of the H1N1 Swine Flu virus, and that is causing a ruckus in the commercial air transport industry. Crews and passengers alike are worried that they will 'catch' the virus on board a plane. Are they right to be so concerned?

I can't completely allay people's fears, but I can relate some scientific information that may help to put the relative risk of catching the swine flu virus on an airplane into perspective. Let me tell you about some things that are known about just how is flu transmitted aboard an aircraft.

Many seem to believe that people aboard passenger aircraft catch the flu and other infectious diseases because much of the cabin air is recirculated. In other words, they believe that the viruses and bacteria that cause infectious diseases are airborne, and that the germs are distributed throughout the aircraft via the recirculated air.

More and more evidence shows this explanation to be false, or at least limited. For one thing, the HEPA filters used in the air circulation systems of modern passenger aircraft are amazingly efficient at trapping particles -- including viruses and bacteria -- before they can be recirculated. But there is another reason, too.

Countless studies -- most of which have been carried out in health care facilities, where there are lots of germs of all kinds -- have shown that infectious diseases are transmitted most often through direct contact with surfaces on which droplets from the sneezes or coughs of an infected person have landed. When droplets land on surfaces, the viruses and bacteria contained in them stay on the surface, even after the droplets dry.

The germs are passed to the hands of other people who subsequently touch those surfaces. This is exactly why frequent and thorough hand washing is so highly recommended as a method of infection control.

Recent information about how flu is transmitted, published in a journal called Lancet Infectious Diseases [reference below], confirms that flu transmission "occurs at close range rather than over long distances, suggesting that airborne transmission, as traditionally defined, is unlikely to be of significance." This conclusion is based on a large-scale review of published data on the subject.

Results from 32 experimental and epidemiological studies were evaluated by a Canadian team from the University Health Network, Toronto for this report. Their analysis showed that the flu virus is indeed more likely to be transmitted to people within a short distance of the infected person, via large respiratory droplets that fall out of the air, and not via "fine aerosols" that hang in the air for extended periods of time.

This information has important implications for crews working aboard passenger aircraft -- especially flight attendants. On the one hand, it is somewhat reassuring to know that the risk for airborne transmission of the flu virus throughout an aircraft is relatively small. On the other hand, it adds more importance to avoiding close contact with an infected person -- and with objects that may have been contaminated by "large respiratory droplets" from that person -- that is, from coughs and sneezes, as well as oral and nasal secretions in general.

The passengers sitting nearest to an infected person are those most at risk for coming into contact with surfaces contaminated by "respiratory droplets" -- seats, tray tables, armrests, and so on. For flight attendants, the greatest risk probably comes from handling items used by an infected person, or from that person's immediate area.

Risk Mitigation

Flight attendants who touch or handle items that have been used by infected people may very readily come in contact with the germs left behind by those "respiratory droplets." Collecting trash, food trays, and other items used by an infected person can put flight attendants at risk for coming into direct contact with infectious agents.

The sensible thing to do would be to wear protective gloves when handling items used by infected passengers. Unfortunately it's not always clear who is infected and who is not. Therefore, if I were running the show (especially during an active outbreak), I would advise flight attendants to wear protective gloves whenever they are collecting used items, and I wouldn't restrict the use of gloves to collecting trash or food trays.

Unfortunately not all air carriers approve of flight attendants wearing gloves, except when they are tending to a passenger who is known to be infected. The trouble is that during an active outbreak such as the present one, it is difficult to know who is infected, and who is not. In fact, people can be infected -- and infectious -- before they begin to feel or display symptoms.

A number of airlines actually prohibit their cabin crew from wearing protective gloves -- on the silliest grounds, I might add. For example, I have been told that some airline managers think that the sight of a flight attendant wearing protective gloves would upset the passengers, because it would suggest that the aircraft was unclean. This is nonsense, and it trivializes a known health risk -- a risk that exists for other passengers, as well as cabin crew.

If you work for a carrier that prohibits or discourages cabin crew from wearing gloves -- especially when collecting food trays and trash -- I would advise you to bring up the issue with your inflight supervisors. Get your union involved, too.

Transmission of infectious diseases aboard an aircraft is an occupational health risk for crews that should not be ignored, yet there are ways to lessen the risk.

Earlier this week, the Association of Flight Attendants-CWA, the largest flight attendant union in the U.S., published a page on their website, Swine Flu: What flight attendants need to know, which includes useful information about the virus that currently is circulating, and ways that cabin crew can protect themselves. Go and have a look at that, as a starting point.

Stay informed about current developments, but choose your information sources wisely. Don't rely solely on news reports, some of which may be inaccurate or have a bias. In the United States, the best source of current, reliable information is the Centers for Disease Control and Prevention (CDC). Here is the link to the CDC's Swine Influenza (Flu) website: http://www.cdc.gov/swineflu/

Another place to look for both background information and current news about the current outbreak is the News & Info About H1N1 Swine Flu page on the AircrewHealth.com website.

Study referenced above: Brankston, G., Gitterman, L., Hirji, Z., Lemieux, C., & Gardam, M. (2007). Transmission of influenza A in human beings. The Lancet Infectious Diseases, doi:10.1016/S1473-3099(07)70029-4.

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RELATED:

• Airline travel and the spread of flu: Implications for the swine flu outbreak - AircrewBuzz.com, Apr. 27, 2009
• Swine Flu (H1N1): Information for Flight Attendants - AircrewBuzz.com, Apr. 28, 2009

Swine Flu (H1N1): Information for Flight Attendants

by B. N. Sullivan

Yesterday I was speaking with a flight attendant about the current outbreak of Swine Flu (H1N1). "The news is so scary, I don't know what to think," she said. "Should I be afraid to go to work or not?"

"No," I told her. "You needn't be afraid to go to work, but you should learn the facts about the disease, and understand what to do to lessen your chances of becoming infected."

It does seem like the swine flu outbreak came out of nowhere and just exploded onto the scene. There are so many rumors circulating, it's no wonder people are scared. The news media jumped on the story quickly, and although they have reported some factual information, they also have fanned the flames of fear -- sometimes by their choice of words, and sometimes by feeding the rumor mill instead of sticking to known facts.

Don't panic. Mixed in among the mass of rumor and hype, there is some good, solid, reliable information -- you just have to know where to look for it.

Here are some good places to start. (Each of these items will open in a new page or tab when you click.)

Background information about Swine Flu (H1N1)

• Key Facts about Swine Influenza - U.S. Centers for Disease Control & Prevention (CDC).
• Swine Influenza (Flu) - CDC, Daily updates
• Swine influenza - World Health Organization (WHO), updated regularly
• PandemicFlu.gov - The official U.S. government Web site for information on pandemic flu (including swine flu)

Travel and Aviation-specific Swine Flu Information

• Swine Flu: What flight attendants need to know - AFA-CWA, April 2009
  
• Interim Guidance to Assist Airline Flight Deck and Cabin Crew in Identifying Passengers Who May Have Swine Influenza - CDC, April 2009
• Interim Guidance for Airlines Regarding Flight Crews Arriving from Domestic and International Areas Affected by Swine Influenza - CDC, April 2009
• Safety Alert for Operators (SAFO): Swine Flu H1N1 Information - FAA, April 2009 [PDF format]
• PandemicFlu.gov - Section on Travel & Transportation - U.S. Dept. of Health & Human Services
• Frequently asked questions – Swine Influenza and Air Travel - IATA, April 2009 [PDF format]
• Suspected Communicable Diease: Guidelines for Cabin Crew - IATA, December 2008 [PDF format]

If and when new information from truly reliable sources becomes available, I will add it to this page.


If you are on Twitter, you can keep abreast of new developments by following @CDCemergency. You can also follow the AircrewHealth.com health news Twitter feed @Twellness. No rumors. No hype. Just facts and links to news you need to know in order to make informed health decisions for yourself and those you care about.

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UPDATE May 1, 2009: Here is something useful. The U.S. Environmental Protection Agency has published a document listing 500 Antimicrobial Products Registered for Use Against Influenza A Virus on Hard Surfaces (17-page PDF).

These include disinfectant solutions and foams, as well as single-use wipes. You might want to check it out and see if the ones you use on aircraft, and pack with you to use on your layovers, are on the list. There is a page on the EPA website that explains.

Airline travel and the spread of flu: Implications for the swine flu outbreak

by B. N. Sullivan

Over the past several days there has been an explosion of news about an outbreak of a new kind of flu virus, Swine Influenza A/H1N1 (AKA swine flu), that began infecting large numbers of people in Mexico, and then spread to several other countries, including the United States. We in the aviation community may not like to admit it, but air travel almost certainly has played a central role in the rapid spread of the disease outside the area where it first emerged.

Even as I write this, countries around the world are initiating screening of passengers arriving at gateway airports in an attempt to detect those who may be carriers of swine flu. Discussions are underway about travel restrictions to and from infected areas. Undoubtedly this outbreak -- and some of the measures being implemented (or at least being considered) -- will have a negative effect on the civilian air transport industry, which is already suffering from the global economic crisis that preceded the emergence of swine flu.

Should restrictions on air travel be imposed? Should public health concerns take precedence over the economic impact on the aviation industry? That's a tough call, and I'm glad I don't have to make it.

What is undeniable is that there is indeed a link between air travel and the spread of flu. That link was established several years ago by some scientists who studied the role of air travel in the spread of seasonal flu. It's an interesting story with great relevance to the present situation.

A team of researchers reviewed public records of deaths across the United States due to flu (influenza) and pneumonia for the nine year period from 1996 through 2005. They were looking for patterns in the timing of deaths attributed to seasonal flu outbreaks, and the geographic spread of flu mortality across the United States.

It is well known that 'flu season' occurs annually during the cooler months of the year, but the researchers wanted to find out more exact information about the timing of this yearly health problem, and about how the flu is spread.

They found that the timing of the peak of the flu season seemed to be related to seasonal patterns of passenger airline travel volume.

Specifically, they found that the seasonal increase in domestic air travel volume that begins around Thanksgiving in the U.S. was quite consistently followed by an increase in the rate of influenza spread. In years when holiday travel volume was lower, influenza spread more slowly. Conversely, during years with higher traffic volume, especially around Thanksgiving, influenza spread across the country more rapidly.

They also found that the volume of international air travel was significantly correlated with when the peak number of flu-related deaths occurred in a given year. They noted that in years when the number of international travelers was lower, especially during early Autumn, the flu season peaked later, and vice versa.

But when they dug a little deeper into the data, they discovered something even more interesting.

The patterns in the first five years they studied were remarkably stable. The timing of the peak number of flu-related deaths occurred in mid-February in each of those years. In fact the actual date when the peak occurred was within two days of February 17th for each of those first five years.

Then 9/11 happened, and we all know what followed in regard to air travel. First there was the ground stop, and when airline schedules resumed, passenger volume was quite low for many months. Then, over the next few years, annual passenger volume gradually increased.

Guess what: rates of spread for flu deaths around the U.S., and the timing of the peak of the flu season during those same years reflected the patterns in passenger volume. During the 2001-2002 season, flu spread across the country more slowly than in any other year of the nine studied, and the peak was weeks later.

Over the next three years, as passenger volume gradually increased, the peak of the flu season gradually moved to an earlier date -- until the final year they studied (2005) when it was right back to February 17th!

In the words of the researchers themselves:

The flight ban in the US after the terrorist attack of September 11, 2001, and the subsequent depression of the air travel market provided a natural experiment for the evaluation of the effect of flight restrictions on disease spread. The importance of airline activity was highlighted by the delayed peak of influenza in 2001-2002 following the period of reduced flying activity. This finding is further validated by the absence of a similar delay in influenza activity in France, where flight restrictions were not imposed.

Of course there are many other factors besides airline travel that can influence the spread of seasonal flu. Nevertheless, the findings of this study do confirm to a certain extent what many have always suspected: that air travel during flu season does indeed figure into how and when the flu is spread.

One final issued raised by this study's results is the extent to which restrictions on air travel might assist in inhibiting the spread of other infectious disease epidemics. Of particular concern these days is the prospect of the spread of swine flu.

In light of the findings from this study about how air travel figures into the spread of seasonal flu, we have to wonder if a similar effect would be found for swine flu, since it can readily be passed from human to human in a manner similar to seasonal flu.

The researchers said, "Our results suggest that limiting domestic airline volume would have a measurable impact on the rate of spread of an influenza pandemic, and particularly on spread across regions."

Given the many other factors that influence the spread of disease in epidemics, they believe that the primary benefit of air travel restrictions during an epidemic or pandemic would be to alter the rate and timing of the spread of the disease, not to prevent it outright. But, in the event of a deadly pandemic, slowing the spread even for a few weeks might give public health officials a bit more time to put in place other measures to fight the disease.

Source: Brownstein JS, Wolfe CJ, & Mandl KD (2006) Empirical Evidence for the Effect of Airline Travel on Inter-Regional Influenza Spread in the United States, PLoS Med 3(10): e401

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NOTE: This is the first in a series of articles about swine flu and air travel that I will post here on AircrewBuzz.com. As a researcher, I have been involved for years with topics relating to the health and well-being of people who work in the civilian air transport industry, and I run a website (AircrewHealth.com) devoted to that subject matter. I am preparing a special page for that website with information about swine flu, tailored to the information needs of people who fly for a living.

More to follow...

Were Flybe cabin crew sickened by fumes in aircraft cabin?

Two cabin crew members became violently ill and collapsed during a recent Flybe flight on a BAe 146 aircraft between Birmingham, England and George Best Belfast City Airport in Northern Ireland. The Transport and General Workers' Union, which represents Flybe's cabin crew, says the crew members' illness was caused by a "toxic gas" in the aircraft cabin. The union is calling for an investigation.

A news article about the incident in the Belfast Telegraph quotes union officials who say this was "the latest in a number of potentially disastrous mid-air incidents in which crew members working for various airlines have become dangerously ill during flights."

Campaigners who believe the incidents are due to deadly toxins from jet engine oil contaminating the air supply have warned that the 'fuming' incidents are putting the long-term health of crew and passengers at risk and are also in danger of causing a major air catastrophe if pilots become incapacitated.

Details have emerged in a CAA report into a terrifying episode last month on board the Flybe jet.

Passengers on board the BAe 146 plane flying into Belfast from Birmingham were completely unaware of the drama at the rear of the aircraft, and of the fears of other terrified cabin crew that they may not have been able to deal with an emergency with incapacitated staff.

Dessie Henderson, senior organiser of the Transport and General Workers' Union in Belfast, says it's just one of an increasing number of 'fuming' incidents which are feared to be leaving airline staff and passengers facing possible long-term health problems due to so-called "aerotoxic syndrome".

Mr. Henderson went on to say, "There have been numerous incidents and they can't continue to go unexplained when the health and safety of the cabin crews and the passengers on board the planes are at stake. If these incidents are down to organophosphates, then that is what the airlines need to be carrying out checks for, to see if their staff and our members have been exposed to it."

While declining to comment on the specific incident, a spokesman for Flybe said that all of the company's aircraft are manufactured and maintained to the highest industry standards.

"Any incidents involving sickness experienced by cabin crew, flight crew or passengers are taken very seriously by the company, with appropriate medical support always provided.

"The statistically very small occurrences of on-board sickness indicate that our systems and processes are robust and more than meet all CAA regulatory demands.

"Flybe are at the leading edge of co-operative joint research in this area and are comfortable that our expertise marks us out as industry leaders."

The UK The Government's Committee on Toxicity is said to be examining the threat from contaminated cabin air.

Contaminants in passenger aircraft cabins

Here's another article on Airport Business that has some attention-grabbing lines:

What if a terrorist released an invisible poison or disease-causing agent such as anthrax inside a commercial airliner?

Researchers at the [Kansas State] university are under contract with the Federal Aviation Administration to study how to detect, contain and remove contaminants on planes.

Oh, good. I'm glad to hear that! The article goes on:

While the airplane research covers accidental contamination and the natural spread of viruses such as flu or chickenpox, the deliberate spread of toxins is a key concern, said project supervisors.

"If we had been doing this research 10 years ago, we probably wouldn't be looking at intentional contamination of the cabin," said Byron Jones, project director and a professor of mechanical and nuclear engineering. "We'd be looking at normal, everyday contaminants."

While someone could release toxins in other crowded environments - such as theaters, stadiums or buses - airplanes are historically terrorist targets and have especially captive occupants. Such an incident would have a "huge negative impact" on the airline industry, Jones said.

Gee, ya think??

Okay, okay. I was being sarcastic there. But seriously, folks, aren't you glad that someone actually is looking into this issue?

Aircraft cabin air quality is indeed a very serious issue, whether we're talking about the spread of infectious diseases by coughing, sneezing passengers, or issues like the spraying of pesticides inside airliner cabins (required by some governments for arriving international flights).

And if you're interested in reading more about the Kansas State University research on aircraft cabin contaminants, you can read the whole article here: Study Seeks Way to Remove Poisons from Airplanes - Airport Business

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