Polio virus Nervous system Polio is a virus

Polio virus • Nervous system: Polio is a virus that infects the nervous system of humans (only) • Paralysis: It can cause temporary or permanent paralysis or death • Vaccine : There is a vaccine for polio • Eradicate : The World Health Organization plans to eradicate polio in the next decade • Continue: Polio outbreaks continue to occur in areas in which many are not vaccinated

• Since vaccine has become widespread in the United States, cases of polio are rare. • However, polio remains a problem in many parts of the world. •

• Poliovirus infects human cells by binding to an immunoglobulin-like receptor, CD 155, (also known as the poliovirus receptor (PVR) on the cell surface • Poliovirus is a positive stranded RNA virus. Thus the genome enclosed within the viral particle can be used as messenger RNA and immediately translated by the host cell.

Immune system avoidance • Poliovirus uses two key mechanisms to evade the immune system. First, it is capable of surviving the highly acidic conditions of the gastrointestinal tract, allowing the virus to infect the host and spread throughout the body via the lymphatic system. • Second, because it can replicate very quickly, the virus overwhelms the host organs before an immune response can be mounted. [5]

polio virus

3 -D image of poliovirus

5 -fold Axis 3 -fold Axis 2 -fold Axis VP 1 VP 2 VP 3

• For decades, no one knew what poliovirus looked like, since viruses cannot be seen under a microscope. In 1985, a team led by James Hogle of Harvard Medical School obtained high-resolution, 3 D images of poliovirus, and today, the newly formed Children's Hospital Boston -- Harvard Medical School structural biology unit is heir to the Enders tradition.

• Led by Stephen Harrison, this group is using a variety of sophisticated tools like X-ray crystallography and molecular electron microscopy to obtain detailed, dynamic, 3 D views -- accurate down to the atom -- of how viruses move, transfer information and reconfigure themselves to attack their victims. These images are shedding light on many of today's viral scourges, such as HIV, dengue and rotavirus, and providing new leads for treatment and vaccine development.

Polio virus

• An ancient Egyptian stele, portraying a prince with a withered leg - probably polio. © WHO/GPEI

Researchers Glimpse Polio Virus as it Enters Host Cell Contact: See for a moment 3 -D structures The image on the left shows a naked polio virus. The polio virus on the right is studded with 60 twig Small thin stem -like structures, the receptors. on a tree

• The polio virus lives in the throat and intestinal tract of infected persons. • The virus enters the body through the mouth, usually from hands contaminated with the stool of an infected person. Objects, such as eating utensils, can also spread the virus. • Food and water are not thought to play a major role in the spread of polio. •

WHO • Polio cases have decreased by 99. 8% since 1988, from an estimated 350 000 cases to 483 in 2001*. The reduction is the result of the global effort to eradicate the disease.

Areas with highintensity transmission • Together, these countries accounted for more than 85% of the new polio caseload in 2001. They are characterized by having areas with large populations and low routine immunization coverage, sub-optimal sanitation and relatively wide geographical distribution of the wild poliovirus. These countries are: • India • Pakistan/Afghanistan • Nigeria/Niger

Symptoms • Not everyone will experience all the symptoms, which vary according to the type of polio one has. In mild polio the symptoms are: • Headache • Nausea/vomiting • General discomfort or slight fever for up to three days.

• In non-paralytic polio, the symptoms are similar to mild polio with the addition of: • Moderate fever • Stiff neck and back • Fatigue • Muscle pain

Individuals with paralytic polio will experience: • • Tremors Muscle weakness Fever Stiffness Constipation Muscle pain and spasms Difficulty swallowing

预防 • 口服脊髓灰质炎减毒活疫苗糖丸(1957年 发明） Oral vaccination with live vaccine • Vaccination programs have • eradicated it from the • Western world and promise • to eliminate it globally Dr Alber Sabin

新进展Date: Thu, 11 Jul 2002 Scientists have built the virus that causes polio from scratch in the lab, using nothing more than genetic sequence information from public databases and readily available technology. The fact proves that even if all the polio virus in the world were destroyed, it Bring would be easily possible to resurrect the back into crippling disease, says Aniko Paul at the use State University of New York at Stony Brook, one of the researchers