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Cytomegalovirus It is one of the common viral infections affecting mainly the low socioeconomic classes. In some countries the seroprevalance rate is over 90 %.
Transmission The virus can be found in blood, saliva, urine, breast milk and genital secretions. Direct person to person transmission through contact with saliva. Vertical transmission- Transplacental and through breast milk Horizontal - through blood transfusion and organ transplant -may also transmit through sexual intercourse
Incubation period The incubation period varies depending on the means of transmissions.
Clinical presentation
Most infections are asymptomatic.
Infectious mononucleosis like symptoms are common. The clinical signs and symptoms include mild fever, sore throat, lymphadenopathy (which is similar to patients with EBV infection or toxoplasmosis) and mild jaundice.
CMV in pregnancy CMV infection can transmit to the unborn baby. Only 40 % of primary infection may result in congenital infections and it can cause congenital abnormality in 10 % of them.. Unlike the other important viral infections in pregnancy, CMV infection acquired in all three trimesters is known to cause morbidity and mortality in the fetus.
Congenital infection Asymptomatic (90%)- only 10 % of congenitally infected children present with signs and symptoms of CMV infection. The common presentations in the first 2 weeks after delivery include Ø Skin rash Ø Jaundice and Hepatosplenomegaly Ø Microcephaly Ø Calcification in the brain Deafness is another complication associated with CMV infection. Affected infants should have a follow up to correct the hearing defects.
CMV in neonates CMV infection can occur during or after delivery. The main presentations include Ø Skin rash Ø Pneumonitis There is no evidence to suggest any neurological problems or hearing defects in infection acquired after delivery. On the other hand immunocompromised children may develop neurological problems, therefore care should be taken to prevent horizontal infection.
CMV in immunocompromised patients The common problems associated with infection in immunocompromised patients include Ø Colitis Ø Pneumonitis Ø Encephalitis and retinitis Ø Hepatitis Ø Bone marrow suppression Reactivation could occur between 1-6 months of transplant. Rare complications There are some reports to suggest some patients with transverse myelitis or Guillain Barre syndrome have evidence of recent CMV infection. Investigations
Depending on the clinical presentations.
Diagnostic tests For patients presented with infectious mononucleosis like illness and Guillain Barre syndrome Serum for CMV IgM
CMV antibody
CMV IgM CMV IgG CMV IgG avidity Acute/ recent infection + + Weak Past infection _ + Strong Reactivation _ + Strong
Congenital abnormality
Maternal blood for CMV IgM or Ddemonstrate seroconversion (use booking blood) Unborn baby- amniocentesis- CMV PCR -cord blood- CMV IgM and PCR
Test for CMV DNA by PCR (appropriate samples include urine and blood sample in EDTA)
It is difficult to identify whether CMV infection has occurred before delivery or after delivery when children present after 3 weeks of life. CMV IgM and CMV DNA PCR can identify children infected with CMV. Blood spots on Guitheri card can be tested for CMV DNA PCR.
NB: Maternal CMV IgG may remain detectable for 6-9 months after delivery.
Immunocompromised patients EDTA blood, Urine, biopsy, BAL and CSF are appropriate specimens for CMV DNA test (by PCR). Blood is the only appropriate sample for monitoring response to therapy. The Viral load in Urine sample may vary depending on the fluid intake.
Screening CMV IgG test is appropriate for screening purpose. Indications for screening includes Ø Before IVF Ø Before transplant Ø HIV infected patients Ø donated blood for transfusion
Treatment Most individuals infected with CMV are asymptomatic and some have mild illness, for these reason the majority of patients do not require antiviral therapy.
Hospital care Treatment with Gancyclovir may be considered for patients with congenital CMV infection with CNS involvement. Some experts advocate its use in infants with colitis as well. Recently, there was a report that suggested neonates with CMV viral load over 100,000 copies/ml have a high chance of developing neurological problems. If other studies support this finding, there is a prospect for the use antiviral to prevent progression of the disease processes in neonate with high viral load.
Gancyclovir is considered to be toxic and should be avoided in pregnancy. Gancyclovir may be used to treat immunocompromised patients with pneumonitis, colitis, retinitis, encephalitis or oesophagitis. Reducing the level of immunosuppression is considered to be more effective than the use of antivirals. CMV specific immunoglobulin is indicated for stem-cell, and lung and cardiac transplant patients if they develop pneumonitis.
Prevention
There is no vaccine. Screening of pregnant women is not recommended as there is no any prevention measure. Screening of patients before transplant and matching donor and recipient has been beneficial. Screening of blood sample and transfusing only seronegative bloods to immunocompromised patients and preterm newborn have reduced the incidence of CMV associated mortalities in these group of patients. Pre-emptive therapy and prophylaxis are useful to prevent disease associated with CMV reactivation.
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Date this page is updated: 04/03/2007 23:13:30 www. virologynotebook.co.uk
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