Air Travel and Disease: Airborne

Air travel has skyrocketed since the first commercial flight took off in 1914. Internationally there were almost 10 million flights last year alone1, carrying over 800 million passengers all over the world3. This massive flow of human traffic has facilitated an unprecedented level of global interconnectedness and made a huge impact on global health.

Health in a globalized world

The new accessibility of the planet has increased the reach of humanitarian relief organizations and scientists. The availability of flights spanning the globe has enhanced the ability of international health organizations, such as Doctors Without Borders and the Red Cross, to respond to health crises, offering on the ground emergency care. Outbreaks receive nearly immediate attention, both from public health officials and scientists. Samples can be shipped within hours, expediting the process of pathogen identification and vaccine development.

There is a downside to the ease of international transport. Like the ships of the great explorers, airplanes provide a means for disease transmission, both as sites for direct transmission and as vectors for foreign pathogens. However, while airplanes do offer a unique opportunity for people (and microbes) from around the world to mingle, they are relatively free from epidemics. In fact, the most common illness contracted on airplanes is food poisoning. A great deal of study and engineering has gone into the development of airplane ventilation and air filtration systems in an effort to reduce infectious disease spread. Unfortunately filters are not mandated on all airplanes, and some amount of transmission will remain despite our best efforts. Nonetheless, the risk of contracting something from a co-passenger is roughly the same as in other confined spaces2.

air travel
Think of this as a mosquito.

Touchdown

More worrying than on-flight transmission is what happens after the airplane lands. It has been speculated that several disease outbreaks, including West Nile Virus in the United States, can be traced back to air travel, either by infected passengers, animals, or insects. Insect vectors (insects that transmit a disease between human or animal hosts), such as mosquitoes, can be unwelcome stowaways on flights from warmer climes. This has led to a phenomenon called airport malaria, a rare occurrence when a traveler who has not been to an affected region gets sick with the disease2.

In a world growing smaller by the day, you may not even need to travel to risk exposure. Western cultural exportation may be spreading the mental illnesses of the West around the world. Mental illness, unlike physical illness, expresses itself in a way that is culturally acceptable. With the dissemination of a western view of mental illness and the Diagnostic and Statistical Manual of Mental Disorders (the DSM, a catalogue of mental illnesses), western illnesses have risen in occurrence globally. At the same time western illnesses are increasing, mental illnesses originating in other cultures are disappearing as they lose visibility4.

Air travel and the globalization that accompanies it has changed the face of global health, shifting the spread of diseases and they way we treat them. It gives us the ability to explore the four corners of the earth, but that opportunity has its risks. This tradeoff highlights one of the scariest realities of disease; its dangers are often hidden until it’s too late.

References

1. Flights, All Carriers-All Flights. Bureau of Transportation Statistics. Web. Accessed 30 September 2013. http://www.transtats.bts.gov/Data_Elements.aspx?Data=2

2. Mangili, A & MA Gendreau. (2005). Transmission of infectious diseases during commercial air travel. Lancet. 365:989-996.

3. Passengers, All Carriers-All Airports. Bureau of Transportation Statistics. Web. Accessed 30 September 2013. http://www.transtats.bts.gov/Data_Elements.aspx?Data=1

4. Watters, E. The Americanization of Mental Illness. The New York Times. 10 January 2010.

Image credit: Creative Commons, http://www.freestockphotos.biz/stockphoto/9260

Smallpox: The First Frontier

Aliases: smallpox

Smallpox could be the poster disease for exploration. It has crisscrossed continents and voyaged over oceans in company as varied as Islamic expansionists, Crusaders, and the explorers of the 16th-19th centuries.

In the age of exploration, smallpox was endemic to (regularly found in) Europe, and parts of Asia, the Middle East and northern Africa. When the people of these regions began to disperse around the globe, colonizing all the ice-free landmasses they could find, they brought with them an unsavory gift: smallpox. This distasteful offering was arguably the most important weapon in the arsenal of the colonial powers, particularly in their forays into southern Africa, Oceania, and the Americas, where the disease devastated the local, previously unexposed populations. Although it is extremely difficult to estimate the number of deaths related to smallpox alone, there are documented occurrences of smallpox epidemics in these “new” lands with mortality rates ranging from 33% to 100%2.

smallpox
Awkward.

Thankfully this grisly legacy is not smallpox’s only connection to October’s theme. The pathogen has also served as humanity’s guinea pig, giving us the means to explore countermeasures, and indeed, an ultimate cure.

As early as 1000 CE, there were attempts to combat smallpox through exposure to the variola virus (its cause) or similar viruses. These and subsequent efforts eventually led to the discovery of the first vaccine by Edward Jenner in 1796. The practice of vaccination was rapidly adopted around the globe, paving the way for future innovations and the use of vaccines against other pathogens. The Smallpox Eradication Programme, led by the World Health Organization, marshaled the power of the smallpox vaccine and successfully eliminated the disease in 1980 (officially; the last naturally occurring case actually happened in 1977)1. This remains the only example of total disease eradication.

Cause: Smallpox is caused by infection by the variola virus. The disease is transmitted directly from person to person through prolonged face-to-face contact (I’m fairly certain that’s CDC code for macking it), contact with bodily fluids or contaminated items, such as clothing or bedding. On rare occasions, smallpox has been transmitted through the air in confined spaces. A person is contagious from the time spots appear until all the scabs have fallen off.

Consequence: After an incubation period of 7-17 days, a person with smallpox will get a high fever, and experience flu-like symptoms (fatigue, body aches, and vomiting). A few days later, red spots will appear in the mouth and throat and spread to the rest of the body. The spots will become raised, then fill with opaque liquid and turn into pustules that are hard to the touch. About two weeks after the spots appear, they will scab over and about a week later, the scabs will fall off, leaving pitted scars.

Cure: There is no cure for smallpox once it has been contracted. Prevention is the only treatment, and there is a highly effective vaccine. Let’s hope that things don’t get weird and we never have to use it again.

References

1. Fenner, F. (1993). Smallpox: Emergence, global spread, and eradication. History and Philosophy of the Life Sciences, 15(3): 397-420.

2. Fenner, F, DA Henderson, I Arita, Z Ježek, & ID Ladnyi. Smallpox and its Eradication. Geneva, World Health Organization, 1988.

3. Smallpox fact sheet: Smallpox disease overview. Centers for Disease Control and Prevention, 30 December 2004. Web. 8 September 2013. http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp

Image source: Creative Commons, https://en.wikipedia.org/wiki/Christian_Radich