Editing Polio (section)

=== Transmission ===
Poliomyelitis is highly contagious. The disease is [[Transmission (medicine)|transmitted]] primarily via the [[fecal–oral route]], by ingesting contaminated food or water. It is occasionally transmitted via the oral–oral route.<ref name="PinkBook2021" /> It is seasonal in [[temperate climate]]s, with peak transmission occurring in summer and autumn. These seasonal differences are far less pronounced in [[tropical climate|tropical]] areas.<ref name="Kew_2005" /> Polio is most infectious between 7 and 10 days before and after the appearance of symptoms, but transmission is possible as long as the virus remains in the saliva or feces. Virus particles can be  excreted in the [[feces]] for up to six weeks.<ref name="ECDC" />

Factors that increase the risk of polio infection include [[pregnancy]],<ref name="Evans_1960">{{cite journal |vauthors=Evans CA |date=December 1960 |title=Factors influencing the occurrence of illness during naturally acquired poliomyelitis virus infections |journal=Bacteriological Reviews |volume=24 |issue=4 |pages=341–52 |doi=10.1128/MMBR.24.4.341-352.1960 |pmc=441061 |pmid=13697553}}</ref> being very old or very young, [[immune deficiency]],<ref>{{Citation |title=Polio and the late effects of polio |url=https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/polio-and-post-polio-syndrome |access-date=2023-04-12 |publisher=Department of Health, State Government of Victoria, Australia |archive-date=12 April 2023 |archive-url=https://web.archive.org/web/20230412211550/https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/polio-and-post-polio-syndrome |url-status=live }}</ref> and [[malnutrition]].<ref>{{cite journal | vauthors = Chandra RK | title = Reduced secretory antibody response to live attenuated measles and poliovirus vaccines in malnourished children | journal = British Medical Journal | volume = 2 | issue = 5971 | pages = 583–5 | date = June 1975 | pmid = 1131622 | pmc = 1673535 | doi = 10.1136/bmj.2.5971.583 }}</ref> Although the virus can cross the [[placenta|maternal-fetal barrier]] during pregnancy, the fetus does not appear to be affected by either maternal infection or polio vaccination.<ref name=UK>{{cite book |veditors=((Joint Committee on Vaccination and Immunisation)), Salisbury A, Ramsay M, Noakes K |title=Chapter 26:Poliomyelitis. ''in:'' Immunisation Against Infectious Disease, 2006 |url=http://www.immunisation.nhs.uk/files/GB_26_polio.pdf |publisher=[[Office of Public Sector Information|Stationery Office]] |location=Edinburgh |year=2006 |pages=313–29 |isbn=978-0-11-322528-6 |archive-url=https://web.archive.org/web/20090326085852/http://www.immunisation.nhs.uk/files/GB_26_polio.pdf |archive-date=26 March 2009 |access-date=9 March 2007 }}</ref> Maternal antibodies also cross the [[placenta]], providing [[passive immunity]] that protects the infant from polio infection during the first few months of life.<ref>{{cite journal | vauthors = Sauerbrei A, Groh A, Bischoff A, Prager J, Wutzler P | title = Antibodies against vaccine-preventable diseases in pregnant women and their offspring in the eastern part of Germany | journal = Medical Microbiology and Immunology | volume = 190 | issue = 4 | pages = 167–72 | date = March 2002 | pmid = 12005329 | doi = 10.1007/s00430-001-0100-3 | s2cid = 12369344 | doi-access = free }}</ref>