In an earlier post,
“The Most Powerful Carcinogen is Entropy,”
I included a pie chart that breaks down cancers in the United States
according to their causes. The numbers almost always take people by
surprise, mostly because of the very small percentage of cases
attributed to synthetic chemicals in the environment. But it is also
striking that relatively few cancers, at least in the developed world,
are caused by viruses.
They seem like such likely culprits. Here is how I describe them in
The Cancer Chronicles:
Existing on the boundary between chemistry and life,
viruses are packets of information— streamlined sequences of DNA or RNA
wrapped in a protective sheath. They are wandering genomes so simple
that some consist of only three genes. Like the handmade Internet
viruses they later inspired, they infiltrate their hosts (the biological
computers called cells) and commandeer the internal machinery. There
the invader’s genes are dutifully duplicated and repackaged again and
again, the viral copies spreading to other cells where they robotically
carry out the same routine—life itself stripped of its capacity to do
anything except reproduce.
Since cancer is a disease of genes gone mad, it is natural to suspect
that viruses would be a primary cause of cancer. But they appear to be
involved in only a few varieties. The most prominent, by far, are liver
and cervical cancer, and the problem is especially fierce in the poorer
parts of the world, which account for about 80 percent of all cases.
Overcrowding and poor sanitation, intravenous drug use, unprotected
sex — all of these are vectors of infection. The lack of medical care —
especially early screening– adds another layer to the problem. While in
the U.S. and other wealthy countries viruses appear to be involved in
about 5 percent of all cancers, in some countries the number can be
as high as 20 percent. (The
worldwide average is about 13 percent.)
These maps, from the World Health Organization, illustrate the divide
between rich and poor. The darker the red, the higher the cancer
incidence.
The most distressing part of the story is that so many of these cancers are preventable.
The main cause of cervical cancer is human papilloma virus. The
widespread use of pap smears has beaten back the disease in the richer
countries. Abnormal, “dysplasic” cells can be identified in the
gynecologist’s office and removed before they mutate further. The HPV
vaccine is set to deliver the final blow.
Liver cancer is a trickier matter. A primary factor is infection by
hepatitis B and C. Those can be targeted through public health programs,
and there is a vaccination for hepatitis B. But early detection of the
cancer itself is highly unlikely. By the time liver cancer manifests
itself, it is usually too late. Another complicating factor — a huge one
— is alcoholism. The scarring of liver tissue from cirrhosis and the
invasion of hepatitis viruses is an especially deadly combination.
Aflatoxin, which is produced by
Aspergillus molds, is another important factor.
Of the hundreds of kinds of cancers, six are responsible for killing
the most people worldwide. The top one is lung cancer caused by
cigarettes. Like cervical and liver cancer it is also preventable. That
leaves stomach cancer, colorectal cancer, and breast cancer. The latter
two might be called cancers of affluence, for they tend to be most
prominent in the wealthier parts of the world. But that is another
story.
For a preview of
The Cancer Chronicles, including the table of contents and index, please see
the book’s website.
Source :
discovermagazine.com
The technology company Garmin recently developed a heads-up
display device for about $130 that works with a mobile app and
Bluetooth-enabled smartphone to project navigation info onto your
windshield. According to the company,
the projection can either go onto a transparent windshield film or an
attached reflector lens. The display can show the distance to the next
turn, speed info, traffic alerts and an estimated time of arrival.
