LETTERS Rapid collaboration between pub- DOI: 10.3201/eid1608.091380 of norovirus infections in society. lic health authorities in the Philippines We therefore present a new approach and Finland led to appropriate action References to estimate the number of cases and at the site of origin of the rabies case spread of norovirus infections in the 1. Meslin FX. Rabies as a traveler’s risk, es- within a few days. In a country in pecially in high-endemicity areas. J Travel community. which rabies is not endemic, diagnos- Med. 2005;Suppl 1:S30–40. We plotted the number of queries ing rabies and implementing control 2. Srinivasan A, Burton EC, Kuehnert MJ, for *vomit* (asterisks denote any pre- measures in healthcare settings are of- Rupprecht C, Sutker WL, Ksiazek TG, et fi x or suffi x) submitted to the search al. Rabies in Transplant Recipients Inves- ten diffi cult because of limited experi- tigation Team. Transmission of rabies vi- engine on a medical website in Swe- ence with this disease. The last human rus from an organ donor to four transplant den (www.vardguiden.se). This num- rabies case in Finland was diagnosed recipients. N Engl J Med. 2005;352:1103– ber was normalized to account for in 1985, when a bat researcher died 11. DOI: 10.1056/NEJMoa043018 the increasing use of the website over 3. Metlin AE, Rybakov SS, Gruzdev KN, after being bitten by bats abroad and Neuvonen E, Cox J, Huovilainen A. An- time and aggregated by week, starting in Finland (5). For imported cases, pa- tigenic and molecular characterization of with week 40 in 2005. We also plotted tient history may be incomplete, but fi eld and vaccine rabies virus strains in the number of norovirus fi ndings per use of RT-PCR for saliva can provide a the Russian Federation. Dev Biol (Basel). week from 16 regional laboratories, as 2006;125:33–7. rapid confi rmation of the diagnosis. To 4. Agreement on the Transfer of Corpses. recorded by the Swedish Institute for support risk assessment and decision Strasbourg (France): Council of Europe; Infectious Disease Control. making, better defi nition of the roles 1973. For the time series on Web search of public health authorities regarding 5. Lumio J, Hillbom M, Roine R, Ketonen L, queries and laboratory fi ndings (Fig- Haltia M, Valle M, et al. Human rabies of a mandate or responsibility to acquire bat origin in Europe. Lancet. 1986;327:378. ure), we fi tted harmonic functions on information concerning international DOI: 10.1016/S0140-6736(86)92336-6 the half-year with no or little activ- ships is needed. ity, defi ning baselines for each series Address for correspondence: Ruska Rimhanen- (1,2). By performing this procedure, Acknowledgments Finne, National Institute for Health and Welfare, we can identify the onset of each ac- We thank Elizabeth Miranda, Vir- Mannerheimintie 166, 00300 Helsinki, Finland; tivity that is assumed to occur when ginia Aguilas, Catalino Demetria, Virgilio email: ruska.rimhanen-fi nne@thl.fi the level rises above the 99% predic- Santos, Joel Rivera, and the personnel of tion interval of the baseline. The week the veterinary virology laboratory at the this increase occurs is shown in the Finish Food Safety Authority for excellent Figure. The Figure also contains the technical assistance; and Marcus Panning, number of media articles on winter Christian Drosten, and the University of vomiting disease provided by a search Bonn for confi rming the RT-PCR result. engine for news in Sweden (www. eniro.se/nyhetssok). By analyzing the Eye-Opening fi gure and investigating the statistical Ruska Rimhanen-Finne, outcomes, we glimpse the prevalence Asko Järvinen, Markku Kuusi, Approach to of norovirus infections in society, as Beatriz P. Quiambao, Norovirus estimated by the search pattern. Fidelino F. Malbas Jr., Surveillance We found 3 striking insights. Anita Huovilainen, First, the onset of vomiting in the Hannimari Kallio-Kokko, To the Editor: It is said that a community precedes the onset of Olli Vapalahti, and Petri Ruutu picture is worth a thousand words. confi rmed norovirus infections in Authors affi liations: National Institute for The Figure illustrates this axiom and healthcare settings. In 3 of the 4 full Health and Welfare, Helsinki, Finland (R. provides several new insights into the seasons investigated, this precedence Rimhanen-Finne, M. Kuusi, P. Ruutu); Hel- spread of norovirus infections. These was 1–4 weeks. Second, the curve for sinki University Central Hospital, Helsinki infections are assumed to greatly af- the Web queries shows much sharper (A. Järvinen, H. Kallio-Kokko, O. Vapalahti); fect society, but little is known about increases and decreases than does the Research Institute for Tropical Medicine, the prevalence of the disease in the curve on the number of reported no- Manila, the Philippines (B.P. Quiambao, F.F. community. Samples sent to labora- rovirus fi ndings. Third, neither search Malbas Jr.); Finnish Food Safety Author- tories usually originate from hospital- behavior nor reporting of positive ity, Helsinki (A. Huovilainen); and Univer- ized persons and thus give a good view tests is driven by media for the winter sity of Helsinki, Helsinki (H. Kallio-Kokko, of the situation in healthcare settings. vomiting disease (confi rmed by a lin- O. Vapalahti) We suspect, however, that these num- bers do not depict the true prevalence ear regression). Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 16, No. 8, August 2010 1319 LETTERS The use of harmonic functions for describing baseline Web searches and laboratory reporting is a simple model, especially because the parameters are estimated by using the half-year with the least activity. Nonetheless, it is a direct approach, and we believe that the method still captures the time of onsets well. Web queries indicate the presence of norovirus infections in communi- ties. Predictions of the onset of the norovirus laboratory reporting should also be possible, but further studies are needed to confi rm that theory. Web queries have previously been correlat- ed with infl uenza (3–7) and have been explored retrospectively for listeriosis (8), Salmonella spp. (9), West Nile virus, and respiratory syncytial virus (10). With the Web queries, we get an additional surveillance system for the time of the year when few norovirus tests are conducted. In addition, know- ing more about the impact of norovi- rus in the community means that we could provide more adequate informa- Figure. Number of queries for *vomit* submitted to a medical Web site (A), number of tion and advocate wiser measures for laboratory-verifi ed norovirus samples (B), with baselines and 99% prediction intervals, and prevention and control. number of media articles about winter vomiting disease (C) in Sweden, 2005–2010. A color version of this fi gure is available online (www.cdc.gov/EID/content/16/8/1319-F.htm). Acknowledgments We thank Bernadette Gergonne for statistical input, Gustaf Rydevik for R sup- In the 2005–06 season, the labo- of the country still showed relatively port, Vårdguiden for granting access to the ratory reporting raised above the de- low virus activity. search logs, and Euroling for realizing the fi ned prediction interval in week 13, Other pathogens such as rotavi- access. much later than the Web queries. This rus, Salmonella spp., Staphylococcus season had no new variants of no- aureus, and Bacillus cereus can cause A.H. was funded by the Swedish Civ- rovirus genotype GII.4. This season vomiting. Usually in Sweden, rotavirus il Contingencies Agency. still showed community infections, infections peak in late winter, and bac- even though few reports came from terial diseases have a minor incidence Anette Hulth, institutions. For the current season compared with norovirus. In our opin- Yvonne Andersson, (2009–10), the interval between on- ion, these other pathogens would not Kjell-Olof Hedlund, set of Web queries and onset of no- interfere with the interpretation of the and Mikael Andersson rovirus infections in hospitals (week results. Author affi liation: Swedish Institute of Infec- 46 and week 1, respectively) was 8 In our routine surveillance of tious Disease Control, Solna, Sweden weeks. In comparison with previous Web queries, we also include other seasons, this delay could mean a low query terms, such as diarrhea and DOI: 10.3201/eid1608.100093 total number of reported cases. How- stomach fl u. However, searches for References ever, in late December, a new variant vomiting show the most distinct pat- of GII.4 affected healthcare settings tern, and vomiting is the most pro- 1. Serfl ing RE. Methods for current statistical in southern Sweden with increasing nounced symptom of a norovirus analysis of excess pneumonia–infl uenza deaths. Public Health Rep. 1963;78:494– norovirus infections, while the rest infection. 506. 1320 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 16, No. 8, August 2010 LETTERS 2. Simonsen L, Clarke MJ, Williamson GD, Possible Recurrent admission was positive. Hemaggluti- Stroup DF, Arden NH, Schonberger LB. nation-inhibition assay demonstrated The impact of infl uenza epidemics on Pandemic (H1N1) mortality: introducing a severity index. a high titer (320) of serum antibody Am J Public Health. 1997;87:1944–50. 2009 Infection, against pandemic (H1N1) 2009 virus DOI: 10.2105/AJPH.87.12.1944 Israel in a blood sample taken at admission. 3. Eysenbach G. Infodemiology: tracking The patient took oseltamivir for 5 fl u-related searches on the web for syndro- mic surveillance. AMIA Annu Symp Proc To the Editor: We report 2 cas- days, and his condition markedly im- 2006:244–8. es of possible recurrent laboratory- proved. Result of a repeat RT-PCR at 4. Polgreen PM, Chen Y, Pennock DM, confi rmed infection with pandemic discharge was negative.