Happy New Year!
The word poliomyelitis means "inflammation of gray
marrow" (Greek: polios, gray, + myelos, marrow, + -itis, inflammation) because the poliovirus destroys nerve cells
(gray matter) in the spinal cord which transmit impulses from the
brain to the muscles. Damage to these cells causes muscle weakness and paralysis. The
virus also destroys nerve cells in the brain. It rarely causes sensory loss.
Paralytic polio typically causes weakness in limb muscles
that is greater on one side of the body (asymmetric). Polio can paralyze the diaphragm
and muscles in the chest, leaving a person unable to breathe. An "iron lung"
is a negative pressure ventilator used to keep people with paralysis of the
respiratory muscles alive.
Poliovirus is transmitted by the fecal-oral route, which means that the virus is shed in the stool of an infected person and then taken into the mouth with contaminated food, water, or other objects, such as fingers that have touched contaminated surfaces. The virus replicates in the back of the throat (oropharynx) and the intestine and then spreads into the blood (viremia).
Less than 1% of people infected with poliovirus develop paralytic polio. More commonly, infected people develop a minor illness called abortive polio: fever, nausea, vomiting, headache, sore throat, fatigue, and malaise with no neurological abnormalities. A small proportion will develop nonparalytic polio (viral meningitis) or polioencephalitis.
Polio was declared eliminated from the U.S. in 1979 and certified eliminated from the WHO Region of Americas in 1994. Today, most parents of infants and most doctors in the
U.S. have never seen a case of polio. I had a great aunt who had polio as a
child. I've seen a few adults in this country with post-polio syndrome, and I've seen children in Africa with atrophied
limbs from polio, but I've never seen an acute
case of polio. It's easy to forget how terrifying polio was in the pre-vaccine era.
OPV is highly effective, inexpensive, and can be
administered by non-medical personnel. There is also a 1 in 2.4 million dose
risk of vaccine-associated paralytic polio (VAPP). There were 144 cases of VAPP
in the U.S. between 1980 and 1998. Because the risk of VAPP outweighed the risk
of wild poliovirus infection in the U.S., the CDC's Advisory Committee on
Immunization Practices (ACIP) first recommended using a sequential IPV-OPV
schedule to reduce the risk of VAPP in 1996 and then an all IPV schedule in
1999. Although OPV is no longer used in this country, the federal government maintains
a stockpile of OPV to use for mass immunization if there is ever an outbreak of
polio in this country.
OPV is used in countries where polio remains endemic or where the risk of importation is greater than the risk of VAPP.
Songwriters Robert and Richard Sherman wrote "A Spoonful of Sugar"
for the 1964 movie Mary Poppins after Robert heard that his children had received
oral polio vaccine on a sugar cube.
References
Sutter, R. W., Kew, O. M., & Cochi, S. L. (2012). Poliovirus vaccine-live. In S. A. Plotkin, W. A. Orenstein, & P. A. Offit (Eds.) Vaccines (6th Ed.). [Electronic version].
Christmas this year was bittersweet. It was Andrew's first
Christmas and our first Christmas without my mother-in-law Mary. Holly and I
also became homeowners last month, although next Christmas will be our first in
our new home.
Andrew received his 4 month immunizations in November: Pediarix®
(diphtheria,
tetanus,
acellular pertussis, hepatitis B,
and inactivated polio vaccine), 13-valent pneumococcal vaccine (PCV-13), Haemophilus influenzae type B conjugate vaccine (Hib), and rotavirus vaccine.
At his 2 month visit in September, Andrew received Pentacel®
(diphtheria, tetanus, acellular pertussis, Hib, IPV) instead of Pediarix®.
The Pediarix® he received this visit won't count as Andrew's third
and final dose of hepatitis B vaccine, but it saved him an extra poke, since he
would have had to have received separate DTaP and IPV shots (Kinrix®,
a combination DTaP and IPV vaccine is licensed for children 4 to 6 years of age).
Poliomyelitis
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Asymmetric weakness:
The muscles in this man's right
leg are atrophied while his left
leg appears normal.
CDC/NIP/Barbara Rice
|
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Mr. Barton Hebert
used this iron lung from the late 1950s until his death in 2003
CDC
|
Less than 1% of people infected with poliovirus develop paralytic polio. More commonly, infected people develop a minor illness called abortive polio: fever, nausea, vomiting, headache, sore throat, fatigue, and malaise with no neurological abnormalities. A small proportion will develop nonparalytic polio (viral meningitis) or polioencephalitis.
Over 95% of people infected with poliovirus have no symptoms
yet still shed the virus and can infect others. Therefore, reported cases of
paralytic polio are only the tip of the iceberg of total poliovirus infections.
 |
My great aunt Gertie had polio
as a child. She could walk
using her hands to move her
feet
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We usually think of improvements in sanitation as reducing
the burden of disease. The opposite occurred with polio in the United States.
Polio had been an infection that was usually acquired in infancy. Because the
infection occurred at a time when babies were still protected by antibodies
they received from their mothers while in the womb (passive immunity), few babies developed polio. As sanitation improved, babies were
no longer exposed to poliovirus and did not develop their own antibodies to the
virus. Children were exposed to poliovirus after they were no longer protected
by maternal antibodies and epidemics began to occur.
During the 1916 polio epidemic in New York City over 9,000 people were paralyzed and 2,343
people died from the disease, most of them young children. Police guarded the
entrances to nearby Hoboken, New Jersey to prevent people from New York from
entering that city. Polio epidemics in the United States increased in size through the first half of
the 20th century. In 1952 there were 57,879 cases of polio reported
in the U.S. After the introduction of the Salk polio vaccine in 1955, the incidence
of polio in the U.S. decreased from 25 cases per 100,000 people every year to
0.4 cases per 100,000 in 1962.
The history of
the development of the Salk
inactivated polio vaccine and Sabin live oral polio
vaccine has been well-documented in books and in the media. I won't go into the
details here, but I've included some links to websites below for those who are
interested and also recommend Paul Offit's book The Cutter Incident.
Polio vaccines
There are two types of polio vaccines used today, inactivated
poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV). IPV is a
killed-virus vaccine that was developed by Jonas Salk and licensed for use in
the U.S. in 1955. IPV is currently the only polio vaccine used in the U.S. It is administered by injection and is
both highly effective and safe.
Oral poliovirus vaccine contains live attenuated (weakened)
poliovirus. Because the vaccine virus replicates in the throat and in the
intestine, it causes a better production of immunoglobulin A (IgA),
an antibody
found on mucosal
surfaces, than IPV. Vaccine virus is also shed in stool and can be transferred
to close contacts of vaccine recipients. OPV was used in the U.S. from the early 1960s until the late 1990s.
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| Administering OPV in Gorakhpur, India CDC/Chris Zahniser |
OPV is used in countries where polio remains endemic or where the risk of importation is greater than the risk of VAPP.
In 1988, the World Health Assembly passed a resolution to eradicate
polio. At that time, there were an estimated 350,000 cases of polio per year in
over 125 countries. Today there are only three countries in which polio remains
endemic; Afghanistan, Pakistan, and Nigeria.
We are closer than ever to eradicating polio from the world forever.
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Polio
cases in the world in 2012
Afghanistan,
Pakistan, and Nigeria are the last remaining polio-endemic countries. Last
year, polio was imported from Nigeria to Chad and Niger, where transmission had
been interrupted.
Global Polio Eradication Initiative
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President Franklin Delano Roosevelt founded the National
Foundation for Infantile Paralysis, now known as the March of Dimes Foundation, to fund polio vaccine research. The U.S. ten cent piece (dime) bears his image for this reason. Roosevelt
contracted polio at the age of 39.
More information
-
History of Polio (Poliomyelitis)
- The Global Polio Eradication Initiative
- Whatever Happened to Polio?
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| Regina Edwards, 1952 March of Dimes |
Centers for Disease Control and Prevention. (2000). Poliomyelitis
prevention in the United States: updated recommendations of the Advisory
Committee on Immunization Practices (ACIP). Morbidity
and Mortality Weekly Report, 49(5), 1-22. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4905a1.htm
Centers for Disease Control and Prevention. (2012). Epidemiology and prevention of
vaccine-preventable diseases (12th Ed.). Washington D.C.: Public
Health Foundation. http://www.cdc.gov/vaccines/pubs/pinkbook/polio.html
Malonado, Y. A. (2009). Polioviruses. In S. S. Long (Ed.) Principles and practice of pediatric
infectious diseases (3rd Ed.) [Electronic version].
Modlin, J. F. (2009). Poliovirus. In Mandell, G. L.,
Bennett, J. E., & Dolin, R. (Eds.). Mandell,
Douglas, and Bennett’s principles and practice of infectious diseases. (7th
Ed.) [Electronic version].
Offit, P. A. (2005). The
Cutter incident: how America's first polio vaccine led to the growing vaccine
crisis. New Haven: Yale University Press.
Plotkin, S. A. & Vidor, E. (2012). Poliovirus
vaccine-inactivated. In S. A. Plotkin, W. A. Orenstein, & P. A. Offit
(Eds.) Vaccines (6th Ed.).
[Electronic version].
Sutter, R. W., Kew, O. M., & Cochi, S. L. (2012). Poliovirus vaccine-live. In S. A. Plotkin, W. A. Orenstein, & P. A. Offit (Eds.) Vaccines (6th Ed.). [Electronic version].
World Health Organization. (2013). Poliomyelitis fact sheet. http://www.who.int/mediacentre/factsheets/fs114/en.
