4 research outputs found
Tracking the spatial diffusion of influenza and norovirus using telehealth data: A spatiotemporal analysis of syndromic data
Background: Telehealth systems have a large potential for informing public health authorities in
an early stage of outbreaks of communicable disease. Influenza and norovirus are common viruses
that cause significant respiratory and gastrointestinal disease worldwide. Data about these viruses
are not routinely mapped for surveillance purposes in the UK, so the spatial diffusion of national
outbreaks and epidemics is not known as such incidents occur. We aim to describe the
geographical origin and diffusion of rises in fever and vomiting calls to a national telehealth system,
and consider the usefulness of these findings for influenza and norovirus surveillance.
Methods: Data about fever calls (5- to 14-year-old age group) and vomiting calls (≥ 5-year-old age
group) in school-age children, proxies for influenza and norovirus, respectively, were extracted
from the NHS Direct national telehealth database for the period June 2005 to May 2006. The
SaTScan space-time permutation model was used to retrospectively detect statistically significant
clusters of calls on a week-by-week basis. These syndromic results were validated against existing
laboratory and clinical surveillance data.
Results: We identified two distinct periods of elevated fever calls. The first originated in the
North-West of England during November 2005 and spread in a south-east direction, the second
began in Central England during January 2006 and moved southwards. The timing, geographical
location, and age structure of these rises in fever calls were similar to a national influenza B
outbreak that occurred during winter 2005–2006. We also identified significantly elevated levels of
vomiting calls in South-East England during winter 2005–2006.
Conclusion: Spatiotemporal analyses of telehealth data, specifically fever calls, provided a timely
and unique description of the evolution of a national influenza outbreak. In a similar way the tool
may be useful for tracking norovirus, although the lack of consistent comparison data makes this
more difficult to assess. In interpreting these results, care must be taken to consider other
infectious and non-infectious causes of fever and vomiting. The scan statistic should be considered
for spatial analyses of telehealth data elsewhere and will be used to initiate prospective geographical
surveillance of influenza in England.