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Author: Aoki Y, et al. Source: J Hosp Infect. 2010 May;75(1):42-6. Epub 2010 Mar 21.


Aoki Y, et al.

Duration of norovirus excretion and the longitudinal course of viral load in norovirus-infected elderly patients.

For norovirus infections, virus-containing stool of infected patients plays an important role as source of infection. A study from Japan shows that, after clinical symptoms have subsided, patients excrete noroviruses for an average of two weeks and thus are a potential risk of infection. On the basis of systematic stool samples, Japanese researchers for the first time investigated for how long infected people excrete viruses after the onset of symptoms and how many viruses are excreted.

Methods: 13 (three male, ten female) people between 60 and 98 years of age took part in the study. All test subjects suffered from a norovirus infection and had positive stool samples. Detection was done by Reverse Transcription (RT) PCR. The participants comprised four from a facility for physically disabled people (Facility A), seven from a geriatric nursing home (Facility B), and two healthy adults working in a laboratory.
Over a time period of six weeks, the patients’ stool was collected and examined per RT PCR for viral load once per week. Due to New Year’s holidays, screenings had to be stopped for two weeks. A total of 63 stool samples were tested for norovirus viral load. Daily observation of clinical symptoms was done by nursing staff, except for the healthy adults, who did the observation themselves.

Results: Most common symptoms included vomiting and diarrhoea, sickness, fever and abnormal fatigue. The clinical symptoms of patients in the Facilities A and B lasted for an average of 3.3 days. The average period of norovirus excretion (period between onset of symptoms and the last positive stool sample) was 14.3 days. Four patients proved to excrete viruses for more than two weeks, one patient even for more than three weeks. No significant relation between older age and duration of virus excretion was determined.

The authors could show that all test subjects excreted noroviruses ten days after the onset of symptoms. With the exception of the two healthy adults, the excretion was even 14 days. Although the study did not draw a link between virus excretion and patients’ infectiousness, the authors recommend applying hygiene management tailored to noroviruses for at least 14 days after the onset of symptoms in a patient. In addition, the scientists suggest to examine the stool of infected patients for viral load 16 days after the onset of symptoms to be able to determine the course of virus excretion for each patient.

J Hosp Infect. 2010 May;75(1):42-6. Epub 2010 Mar 21.

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