on 11-May-2025 (Sun)

backpropagation training algorithm

The general algorithm is as follows: 1. Present a training input pattern and propagate it through the network to get an output. 2. Compare the predicted outputs to the expected outputs and calculate the error. 3. Calculate the derivatives of the error with respect to the network weights. 4. Adjust the weights to minimize the error. 5. Repeat

Classic measles with cough, coryza, conjunctivitis, Koplik spots, and a maculopapular rash beginning on the face is easily diagnosed clinically. Often, there is a striking leukopenia, perhaps related to the infection and death of leukocytes.

A laboratory diagnosis may also be helpful in cases of possible atypi- cal measles or when unexplained pneumonia or encephalitis occurs in an immunocompromised patient.

The differential diagnosis of measles includes rubella, Kawasaki syndrome, scarlet fever, roseola, infectious mononucleosis and rickettsial, enteroviral, and adenoviral infections

Immunofluorescent examination of cells from nasal exudates or from urinary sediment for the presence of measles antigen may be useful for rapid diagnosis of measles.124,130

A commonly used laboratory diagnostic method is the serologic response to the virus. A fourfold or greater increase in measles anti- body titer in acute and convalescent serum specimens is considered diagnostic for measles

SSPE may be diagnosed by the demonstration of high measles antibody titers in serum and CSF in the presence of a compatible illness.130

The ELISA is sensitive and simple to perform and is now widely used.132,133 This assay can also be adapted to detect specific immuno- globulin M (IgM) antibody134 and is therefore useful for the diagnosis of acute measles on one serum sample. False-negative and false-positive results, however, may occur with this assay. Measles IgM persists for as long as 1 month after disease onset.

Included in the group of persons for whom passive immunization is recommended are those who are at high risk for developing severe or fatal measles, are susceptible, and/or have been exposed to the infection. This includes children with malignant disease, particularly if they are receiving chemotherapy, radiotherapy, or both, and children with significant deficits in cell-mediated immunity, including patients with AIDS.

To be effective, passive immunization must be given within 6 days after an exposure; administration after 6 days would not be expected to influence the course of the disease

Babies younger than 1 year (including newborns whose mothers have measles) are also at increased risk after an exposure to measles.

For a healthy infant who has been exposed to measles, the modifying dose of immune globulin is 0.5 mL/kg intramuscularly (IM). An infant passively immunized in this fashion should be given live measles vaccine at age 15 months.128 Immunocompromised children should receive a similar dose of immune globulin, with a maximum of 15 mL

In situations in which the incidence of natural measles before the age of 1 year is high, live measles vaccine may be given at 6 to 9 months of age but should be routinely followed by additional doses.46

Vaccination is not usually recommended for infants younger than 12 months because the induction of immunity may be suppressed by residual transplacentally acquired antibodies.

For individuals who were passively immu- nized after an exposure to measles, vaccination should not be performed for 6 months after a dose of 0.5 mL/kg.128

Transient fever and rash develop about 1 week after vaccination in 5% to 15% of children

A number of reasons for apparent primary vaccine failures of measles vaccine have been proposed.25 These include improper storage of vaccine at temperatures exceeding 4°C, failure to use the proper diluent for the lyophilized vaccine, exposure of the vaccine to light or heat, and vaccination in the presence of low levels of passive antibody.

Although the potential risks of measles vaccine in these children are unknown, they are less than the disease itself. It is currently recommended that children with known asymptomatic HIV infection receive measles vaccine after the age of 12 months.116,128 The use of measles vaccine should also be considered for children with known HIV infection who manifest symptoms if their CD4 T-cell levels are relatively well preserved, especially if they live in locations where there may be transmission of measles, such as certain inner city areas.128

Children who have been treated for malignant disease may be given measles vaccine 3 months after they complete their course of therapy.128

High-risk children, such as those described, may be given monovalent measles vaccine or MMR, but they should not be given MMRV vaccine, which contains a significantly higher dose of the varicella component. No safety data for MMRV in high-risk children are available.151

Serious hypersensitivity reactions to measles vaccine in persons allergic to egg protein have been reported. At one time it was recom- mended that persons with a history of anaphylactic reactions after the ingestion of eggs should be vaccinated only with extreme caution.152 More recent studies, however, have indicated that it is safe to immunize such children.153

Susceptible persons who are exposed to measles, with the exception of young infants, pregnant women, and immunocompromised persons, may be given live measles vaccine to prevent disease, as an alternative to immune globulin. If the vaccine is given shortly after exposure, clinical cases of measles may be prevented because clinical manifestations associated with measles vaccine occur in about 7 days, compared with an incubation period of 10 days for clinical measles.20

Bacterial superinfection should be promptly treated with appropriate antimicrobials, but prophylactic antibiotics to prevent superinfection are of no known value and are therefore not recommended.

Administration of vitamin A has been reported to reduce seroconversion in vaccinees and should therefore be avoided at or after immunization.173

The efficacy of ribavirin administered intravenously or by aerosol for treatment of severe measles is unproven.125,136,174

Vitamin A, 200,000 IU administered orally to children once daily for 2 days, has been reported to decrease the severity of measles, especially in those with vitamin A deficiency.169–171