Viruses cannot reproduce by themselves and therefore infect cells to use the cell machinery to produce more virus. Different viruses have genetic material as single- or double-stranded RNA or DNA. The infectious virus particle is called a "virion" and is the genetic material packed in a protein shell. Viruses come in many genetic sizes, as little as 4 proteins up to 200 proteins.
Hepatitus B virions (Image: CDC USA)
Many different types of viral infections can have impacts on development, either directly by the infection or indirectly by fever and other side-effects of infection.
Rubella virus "German Measles" infection during pregnancy is one of the most serious causing congenital rubella syndrome with serious malformations of the developing fetus. (More? see Rubella page)
Some early postnatal viral infections can also impact upon development and have been the target for worldwide immunization and eradication. (More? see Polio)
Human Immunodeficiency Virus (HIV) leads to AIDS and according to United Nations 2005 data about 38.6 million people had HIV. Of the 17.3 million women infected with HIV, 3.28 million gave birth each year (mostly in sub-Saharan Africa), leading to 700,000 new infections of HIV in children each year. (More? Human Immunodeficiency Virus)
Note also that many cancers can be caused by viruses (papilloma viruses, hepatitis B and C viruses, Epstein-Barr virus and human T-cell lymphotropic virus). Virus-induced cancers account for about 20% of worldwide cancer incidence.
In a few developing countries, and mainly in Africa, at least 3 viruses induce a hemorrhagic fever: Ebola hemorrhagic fever, Marburg virus disease, and Lassa fever.
Page Links: Introduction | Some Recent Findings | Rubella Images | Cytomegalovirus | Herpes Simplex Virus | Hepatitis Virus | Human Immunodeficiency Virus | Avian Influenza Virus | Lassa Virus | Adenovirus | Influenza Virus | References | WWW Links | Glossary
Coll O, Suy A, Hernandez S, Pisa S, Lonca M, Thorne C, Borrell A. Prenatal diagnosis in human immunodeficiency virus-infected women: a new screening program for chromosomal anomalies. Am J Obstet Gynecol. 2006 Jan;194(1):192-8.
Ornoy A, Tenenbaum A. Pregnancy outcome following infections by coxsackie, echo, measles, mumps, hepatitis, polio and encephalitis viruses. Reprod Toxicol. 2006 May;21(4):446-57.
Below is a list of some known maternal, then fetal and postnatal infections that impact upon development.
Only a very brief overview is given, for more details see the listed internal and external links.
Rubella virus (Latin, rubella = little red), also known as "German Measles" (due to early citation in German medical literature), infection during pregnancy can cause congenital rubella syndrome (CRS) with serious malformations of the developing fetus. The type and degree of abnormality relates to the time of maternal infection.
Rubella Virus, transmission electron micrograph (Image: CDC USA)
(More? see Rubella page)
Immunoflourescent detection of Cytomegalovirus (Image: CDC USA)
Viral infection causes systemic infection and extensive brain damage and cell death by necrosis.
Links: Medical Microbiology- Cytomegalovirus | Search Medical Microbiology "Cytomegalovirus"
Viral infection causes systemic infection and extensive brain damage and cell death by necrosis.
Herpes Virus, transmission electron micrograph (Image: CDC USA)
(More? UNSW Embryology - Herpes Simplex Virus)
NCBI Bookshelf (external link) Search Medical Microbiology "Herpes Simplex Virus"
Search PubMed: term = Herpes Simplex Virus teratology | embryo infection | fetal infection | neonatal infection
Viral infection causes paralysis and death affecting mainly children under the age of 3.
(More? UNSW Embryology - Polio)
The human immunodeficiency virus (HIV) is a retrovirus that causes Acquired Immunodeficiency Syndrome (AIDS). Maternal transmission of HIV can occur perinatally in utero, during labour and delivery, or postnatally through breastfeeding and can be reduced by the use of antiretroviral treatment and avoidance of breastfeeding.
Neonatal infection diagnosis can be made by PCR from 6-12 week.
Human Immunodeficiency Virus, transmission electron micrograph (Image: CDC USA)
UNAIDS, the Joint United Nations Programme on HIV/AIDS, estimated that 38.6 million people had HIV (2005), 17.3 million were women. About 3.28 million pregnant women infected with HIV give birth each year (the majority in sub-Saharan Africa) leading to 700,000 new infections of HIV in children each year. (text modified from Gray and McIntyre, BMJ 2007;334:950-953)
Pubmed Coll O, Suy A, Hernandez S, Pisa S, Lonca M, Thorne C, Borrell A. Prenatal diagnosis in human immunodeficiency virus-infected women: a new screening program for chromosomal anomalies. Am J Obstet Gynecol. 2006 Jan;194(1):192-8.
Search PubMed: term = Human Immunodeficiency Virus teratology | embryo infection | fetal infection | neonatal infection
Links: British HIV Association Guidelines for management of HIV and hepatitis C coinfection in adults |
Guidelines for the management of HIV infection in pregnant women and the prevention of mother-to-child transmission of HIV, 2005 |
Guidelines for management of HIV and hepatitis B coinfection in adults |
World Health Organization HIV-infected women and their families: psychosocial support and related issues. A literature review. 2003
Hepatitis (inflammation of the liver) is caused by one of 5 viruses (A, B, C, D, E). "All of these viruses can cause an acute disease with symptoms lasting several weeks including yellowing of the skin and eyes (jaundice); dark urine; extreme fatigue; nausea; vomiting and abdominal pain. It can take several months to a year to feel fit again." (CDC text).
Hepatitus B virions (Image: CDC USA)
Virus particles measure 42nm in overall diameter and contain a 27nm diameter DNA-based core.
Fetal Effects
Hepatitis B virus has a high rate of vertical transmission causing fetal and neonatal hepatitis.
Hepatitis A, C and E are rarely transmitted trans-placentally; if transmitted, they may cause hepatitis.
"There is no evidence that immunization in pregnancy against these diseases (with attenuated viruses) may adversely affect pregnancy outcome."
(Data: Ornoy A, Tenenbaum A. Pregnancy outcome following infections by coxsackie, echo, measles, mumps, hepatitis, polio and encephalitis viruses. Reprod Toxicol. 2006 May;21(4):446-57.)
References:
Ornoy A, Tenenbaum A. Pregnancy outcome following infections by coxsackie, echo, measles, mumps, hepatitis, polio and encephalitis viruses. Reprod Toxicol. 2006 May;21(4):446-57.
Lee C, Gong Y, Brok J, Boxall EH, Gluud C. Effect of hepatitis B immunisation in newborn infants of mothers positive for hepatitis B surface antigen: systematic review and meta-analysis. BMJ. 2006 Feb 11;332(7537):328-36.
Search PubMed: term = Hepatitis Virus teratology | embryo infection | fetal infection | neonatal infection
In 1997 the first instance of direct bird-to-human spread of influenza A (H5N1) virus was documented during an outbreak of avian influenza among poultry in Hong Kong.
Avian Influenza virion (Image: CDC USA)
The virus caused severe respiratory illness in 18 people (6 died) and there have been subsequent instances of other H5N1 infection. The virus does not typically infect humans, and there is no evidence yet of an efect on development.
Marburg RNA virus of the filovirus family, causes hemorrhagic fever in both humans and non-human primates and is a very rare. Virus has characteristic "Shepherd’s Crook" shape.
Marburg virions (Image: CDC USA)
Lassa virus of the arenaviridae family, a single-stranded RNA virus. The virus is the causative agent of a hemorrhagic fever and can be transmitted between species (zoonotic). Death rates are high for women in the third trimester of pregnancy. Fetal death (95%) occurs in uterus of infected pregnant mothers.
Lassa virions (Image: CDC USA)
(More? UNSW Embryology - Lassa virus)
Adenoviruses have a double-stranded linear DNA structure. This virus family is the causative agent of membrane infections in: respiratory tract, eyes, gastrointestinal tract, and urinary tract.
Modified adenovirus is currently used as a research tool to introduce genes into cells in vitro and in animal systems.
Links: Medical Microbiology - Adenoviruses | Search Medical Microbiology "adenovirus"
References:
Gordon JW. Adenovirus gene transfer vector toxicity to mouse embryos: implications for human IVF. Hum Reprod. 2002 Sep;17(9):2380-7.
The possible teratogenic effect of influenza viruses (orthomyxoviruses, "flu") is unclear, with very little evidence directly linking the two events. A recent study did not identify any placental transmission of influenza virus during the second and third trimester.
Irving WL, James DK, Stephenson T, Laing P, Jameson C, Oxford JS, Chakraverty P, Brown DW, Boon AC, Zambon MC. Influenza virus infection in the second and third trimesters of pregnancy: a clinical and seroepidemiological study. BJOG. 2000 Oct;107(10):1282-9.
"We found no evidence for transplacental transmission of influenza virus or auto-antibody production in pregnancies complicated by influenza infections. There was an increase in the complications of pregnancy in our influenza cohort."
Postnatally, the limited neonatal immune system makes postnatal infection dangerous.
References:
Brankston G, Gitterman L, Hirji Z, Lemieux C, Gardam M. Transmission of influenza A in human beings. Lancet Infect Dis. 2007 Apr;7(4):257-65.
Links: Medline Plus - Flu | Search Medical Microbiology "orthomyxovirus"
The Australian NHMRC (1988) recommends neonates be assessed for follow-up care under the following conditions.
(see the NHMRC WWW Page)
CDC (USA)
Public Health Training Network Epidemiology and Prevention of Vaccine-Preventable Diseases (viewable Webcasts requires Media Player) |
Advisory Committee on Immunization Practices (ACIP) Recommendations
Royal College of Obstetricians and Gynaecologists (UK)
Infection and Pregnancy - study group recommendations (Jun 2001)
Reviews | Articles | Search NCBI Bookshelf | Search PubMed | Glossary
Reviews
Degani S. Sonographic findings in fetal viral infections: a systematic review. Obstet Gynecol Surv. 2006 May;61(5):329-36.
Ornoy A, Tenenbaum A. Pregnancy outcome following infections by coxsackie, echo, measles, mumps, hepatitis, polio and encephalitis viruses. Reprod Toxicol. 2006 May;21(4):446-57.
Giles ML, Garland SM, Grover SR, Lewin SM, Hellard ME. Impact of an education campaign on management in pregnancy of women infected with a blood-borne virus. Med J Aust. 2006 Apr 17;184(8):389-92.
Kriebs JM. Changing the paradigm: HIV in pregnancy. J Perinat Neonatal Nurs. 2006 Jan-Mar;20(1):71-3.
Bailao LA, Osborne NG, Rizzi MC, Bonilla-Musoles F, Duarte G, Bailao TC. Ultrasound markers of fetal infection part 1: viral infections. Ultrasound Q. 2005 Dec;21(4):295-308.
Slowik MK, Jhaveri R. Hepatitis B and C viruses in infants and young children. Semin Pediatr Infect Dis. 2005 Oct;16(4):296-305.
Articles
Revello MG, Zavattoni M, Furione M, Fabbri E, Gerna G. Preconceptional primary human cytomegalovirus infection and risk of congenital infection. J Infect Dis. 2006 Mar 15;193(6):783-7.
Search NCBI Bookshelf: prenatal viral infection | Medical Microbiology - prenatal viral infection
Search PubMed: Search May 2006 "prenatal viral infection" 2,710 reference articles of which 441 were reviews.
Search term = prenatal viral infection | rubella virus | Cytomegalovirus | Herpes Simplex Virus | Polio |
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Alcohol "Fetal Alcohol Syndrome"
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cytomegalovirus
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These links require online access to Merck Manuals on Women's Health Issues. http://www.merck.com/mrkshared/mmanual_home2/sec22/sec22.jsp
Risk Factors Present Before Pregnancy
Risk Factors That Develop During Pregnancy
Diseases that complicate Pregnancy
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>Surgery During Pregnancy
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see also Normal Childhood Development
You should look at normal development of the effected systems in the embryo. Development Notes
Alternatively, go on to look at Systematic Development of organs and tissues.
For those wanting to see dynamic processes of development (and have a reasonably quick connection) then the Movies pages are good for watching changes occur.
The study of human development has relied extensively on studying the process in other model animals. For those wanting to see the process of development in other species then the other embryos pages are a good start.
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Maternal infections can impact on normal development. These effects can be directly by virus crossing the placental barrier and infecting the developing embryo, or indirectl due to the impact on the mother, for example the effects of fever.
Often the developmental impact can be variable, depending on the time during development that the infection takes place, the "critical periods".
More recently there has been great concern with viruses which appear to now be crossing species and i nfecting humans, the "bird flu", which could have dire consequences in this global community in which we now live.
This page lists a few know viruses that can impact upon development.
Please email Dr Mark Hill if you wish to make a comment about this current project.