H1N1 Virus Spreads Easily by Plane (Science Daily)

[Guest guest]

H1N1 Virus Spreads Easily by Plane

ScienceDaily (Jan. 8, 2010) — Viruses love plane travel. They get to fly around

the world inside a closed container while their infected carrier breathes and

coughs, spreading pathogens to other passengers, either by direct contact or

through the air. And once people deplane, the virus can spread to other

geographical areas.

Scientists already know that smallpox, measles, tuberculosis, seasonal influenza

and severe acute respiratory syndrome (SARS) can be transmitted during

commercial flights. Now, in the first study to predict the number of H1N1 flu

infections that could occur during a flight, UCLA researchers found that

transmission during transatlantic travel could be fairly high.

Reporting in the current online edition of the journal BMC Medicine, Sally

Blower, director of the Center for Biomedical Modeling at the Semel Institute

for Neuroscience and Human Behavior at UCLA, along with Bradley Wagner and

Coburn, postdoctoral fellows in Blower's research group, used novel mathematical

modeling techniques to predict in-flight transmission of the H1N1 virus.

They found that transmission could be rather significant, particularly during

long flights, if the infected individual travels in economy class. Specifically,

two to five infections could occur during a five-hour flight, five to 10 during

an 11-hour flight, and seven to 17 during a 17-hour flight.

" Clearly, it was air travel, by transporting infectious individuals from the

epicenter in Mexico to other geographic locations, that significantly affected

the spread of H1N1 during the outbreak last spring, " Coburn said. " However,

until our study, it hadn't been determined how important in-flight transmission

could be. Therefore, we decided to make a mathematical model and predict what

could be expected to occur during a flight. "

Using methods from the field of quantitative microbial risk assessment, the

researchers determined the number of potential infections in one transatlantic

flight, assuming there was just a single infected passenger on board.

Specifically, they used the long-established Wells-Riley equation, which was

developed more than 30 years ago and is now standard for predicting the size of

outbreaks within buildings and other enclosed environments for infectious

pathogens transmitted through the air. The equation is based on the number of

exposed individuals, the respiratory rate of the infected person, the length of

exposure to the infectious droplets and the concentration of infectious viral

particles over time.

Within an aircraft, the concentration of particles over time is determined by

ventilation rates, the volume of the cabins in the aircraft and how sick the

infected person is.

" Importantly, we found that the number of infections that would occur on a

flight was very dependent on which cabin the infected individual was sitting

in, " Blower said. " We found that many infections could occur if the infected

individual was traveling in economy class but relatively few if the individual

was traveling in first class. "

So why do more infections occur in economy?

" Primarily, it's the more crowded conditions in economy, " Coburn said. " And

unfortunately, there is a very high probability -- 75 percent -- that if an

infected person is on board, they will be in the economy cabin. "

The researchers note that their results have important implications for

understanding and predicting the global dissemination of H1N1, suggesting that

air-travel restrictions may be useful in controlling influenza pandemics.

" Our results imply that one individual traveling by plane, by infecting other

travelers on the same flight, could cause multiple simultaneous outbreaks in

different geographic locations rather than causing only one outbreak, " Wagner

said. " For that reason, quarantining passengers who travel in economy class on

long-haul flights could potentially be an important control strategy this

winter, but there is no point quarantining passengers in first class. "

The research was funded by the National Institutes of Health and the Simon

Guggenheim Foundation. The authors report no conflict of interest.

Story Source: Adapted from materials provided by University of California - Los

Angeles.

http://www.sciencedaily.com/releases/2010/01/100107114724.htm