Monday, June 20, 2011

Diarrhea Case 5

An 11-month-old girl who attends a day care center develops vomiting and severe, watery diarrhea. The child is taken to an emergency department on the third day of the illness, because the mother is concerned that she has not been able to hold any food or liquids down without vomiting. Physical examination demonstrates an obviously ill child with listless behavior, Ioss of skin turgor, dry mucous membranes, and weight 3 pounds less than 1 week previously. Her blood pressure is 64/40 mm Hg.
Q 1
Which of the following is the most common cause of viral gastroenteritis in children under the age of three?
/ A. Astrovirus
/ B. Calicivirus
/ C. Enteric adenovirus
/ D. Norwalk virus
/ E. Rotavirus
Q 2
In the United States, this virus tends to cause illness during which of the following periods?
/ A. Predominately fall months
/ B. Predominately spring months
/ C. Predominately summer months
/ D. Predominately winter months
/ E. Year-Iong with no seasonal preference
Q 3
The virus is predominately spread by which of the following routes?
/ A. Contaminated blood
/ B. Contaminated food
/ C. Contaminated water sources
/ D. Direct fecaI-oral route
/ E. Inhaled aerosols
Q 4
This child's poor skin turgor, dry mucus membranes, significant weight loss, and low blood pressure all suggest which of the following?
/ A. Dehydration
/ B. Disseminated intravascular coagulation
/ C. IIeus
/ D. Sepsis
/ E. Starvation
Q 5
In 1989, the FDA Iicensed a live attenuated vaccine against the causative agent of this disease for use in infants. It was later withdrawn for
which of the following reasons?
/ A. Data suggested a link between the vaccine and intussusception in some infants during the first 1-2 weeks following vaccination.
/ B. It was questioned if there was association between the vaccine and the development of autism.
/ C. Seizures occurred in a significant number of recipients.
/ D. The vaccine was not widely used because it was too expensive.
/ E. The vaccine was thought to be associated with the development of arthritis in recipients.
Diarrhea Case 5 Answers
The correct answer is E. The most common cause of severe dehydrating diarrhea in infants and young children is Group A rotavirus. The peak incidence of infection occurs from 3 to 15 months. After age three, severe diarrhea is rare, but mild disease can occur. This virus accounts for about half of the cases of diarrhea requiring hospitalization in children in the United States. Rotaviruses are in the Reoviridae family and have a genome consisting of 11 double-stranded RNA segments. The other agents listed can also cause viral gastroenteritis in children and/or adults.
The correct answer is D. In temperate climates, rotavirus has a winter seasonal pattern. In the United States, epidemics occur from November to April. In tropical climates, disease caused by rotavirus occurs year round.

The correct answer is D. Rotavirus is a notoriously contagious virus, and the infective dose is thought to be as small as 10-100 infectious viral particles. While the initial yearly source of the virus may be from contaminated estuary waters (choice C), the vast majority of cases are spread from person to person via direct contact with stool on diapers, objects such as toys, or fingers. While not always necessary, the presence of rotavirus can be confirmed by using enzyme immunoassay on stool specimens. Day care centers are notorious sources of minor epidemics of the virus, and day care workers should be encouraged to be very careful. Reasonable precautions include removal of kids with diarrhea from the day care environment, prompt diaper changing before the children have a chance to touch the stool, and routine use of fresh disposable gloves during diapering.
Contaminated blood (choice A) and inhaled aerosols (choice E) are not usual routes of infection.
Contaminated food (choice B), typically contaminated by food handlers who have recently changed an infected child's diapers, is an uncommon source of infection.

The correct answer is A. These findings strongly suggest that the child is severely dehydrated and in need of intravenous fluid replacement. Approximately 500,000 children are seen in emergency room and outpatient clinic visits for rotavirus infection yearly, and of these, about 50,000 hospitalizations (usually to correct dehydration) and 20 deaths (usually caused by failure to correct the dehydration in a timely fashion) occur yearly in the United States. World-wide, rotavirus infection is thought to cause around 600,000 deaths, primarily in young children. This child with severe dehydration should at least be given IV fluids, and might require hospitalization.

Disseminated intravascular coagulation (choice B) would cause multiple petechiae and purpura, and does not usually complicate rotavirus infection.
Ileus (choice C) is a paralyzed bowel, which is the opposite of the problem seen in gastroenteritis.
Sepsis (choice D) is not usually diagnosed in viral infections, but is seen in severe bacterial infections, often with bacteremia.
Three or four days of not eating is not long enough to induce starvation (choice E).
The correct answer is A. The live attenuated rotavirus vaccine was a virus mixture of reassorted strains that were primarily animal viruses except for one human-virus gene segment. The vaccine had a 49-68% efficacy against any diarrhea due to rotavirus and a 61-100% efficacy against severe disease. However, during the first 11 months of use, post-licensure studies identified intussusception, a form of intestinal obstruction in which a segment of the bowel prolapses into a more distal segment, as an uncommon but potentially life-threatening side effect. Follow up studies estimated that 1 additional case of intussusception occurred for every 5,000- 10,000 vaccinees. The vaccine has currently been withdrawn from use in the US.


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