From January to March 2011, 39 cases of tularaemia  were diagnosed in three counties in central Norway:  21 cases of oropharyngeal type, 10 cases of glandular/ulceroglandular type, two of respiratory and two  of typhoid type. Three cases were asymptomatic and  clinical information was unavailable for one case. The  mean age was 40.3 years (range 2-89 years). Thirty- four reported use of drinking water from private wells.  An increased rodent (lemming) population and snow  melting may have led to contamination of the wells  with infected rodents or rodent excreta. From 1 January to 25 March 2011, 39 confirmed cases  (16 female and 23 male) of tularaemia were reported  from the counties of Sr-Trndelag (28 cases), Mre og  Romsdal (5 cases) and Nord-Trndelag (6 cases) in cen- tral Norway. A confirmed case was defined as a person  who had clinical symptoms compatible with tularaemia  or had used drinking water from the same source as a  previous case, and in whom Francisella tularensis infection was confirmed by a laboratory test as described  below. The cases were geographically scattered within  each county, involving 13 different municipalities  (Figure), and were not linked to one common source.  In comparison, seven cases were reported in total  from other parts of the country in the same period. In  2009 and 2010 four and eight cases respectively were  reported from central Norway.   Tularaemia is a zoonotic disease caused by the bac- terium F. tularensis. Four F. tularensis subspecies are  recognised: tularensis, holarctica, mediasiatica and  novicida. In Europe, the infection is due to subspecies  holarctica which causes in general less severe disease  than subspecies tularensis, which is common in North  America. Several vectors may be involved in transmit- ting the disease to humans, commonly rodents and  hares, but infection may also be transmitted via insect  bites [1]. Several clinical forms are recognised, with oropha- ryngeal and ulceroglandular disease being the  most common clinical presentations in Norway [2].  Oropharyngeal disease is commonly associated with  contaminated food and water, while ulceroglandular  forms are more often seen when there has been skin  contact with infected animals or after insect bites [3]. Outbreaks of oropharyngeal tularaemia have previ- ously been reported from several European countries  [3,4]. Tularaemia is a notifiable disease in Norway  and during the past 10 years, three outbreaks were  reported in Norway [5-7] and all were associated with  water sources in areas where dead lemmings (Lemmus  lemmus) had been observed previously. From 2001  to 2010, between three and 66 cases of tularaemia  were reported annually in the whole country, with an  increase from 16 to 32 cases on average (data avail- able from: www.msis.no). This increase may in part be  explained by the outbreaks mentioned above. Diagnosis and clinical presentation In the outbreak described here, the most common clini- cal presentation was fever and pharyngitis (oropharyn- geal type, 21 cases) and cervical lymphadenopathy  (glandular/ulceroglandular type, 10 cases). Among the  remaining eight tularaemia cases, two were classified  as respiratory and two as typhoid type, while three  were asymptomatic and clinical information was una- vailable for one case. The diagnosis was primarily established by serology  (microagglutination and an in-house IgG/IgM Elisa) in  30 patients [8], by F. tularensis specific PCR analysis  in seven patients [9] and by blood culture (BactAlert,  BioMerieux) in two patients. The two bacterial isolates  were verified as F. tularensis by PCR and sequencing of  the 16S rDNA gene, and confirmed as non-subspecies  tularensis by pdpA PCR [10].  2 www.eurosurveillance.org Thirty-four of the 39 diagnosed cases had been drinking water from a private well or a stream. F. tularensis  DNA was detected by PCR in filtered water from five  different wells tested in Sr-Trndelag. Seven cases in  one municipality were linked to the same water source.  Apart from that, only two cases have been confirmed  to share a common well so far. Follow-up serology has  been recommended for several of the persons exposed  to some of the putative water sources. Discussion The current outbreak involves a large number of munic- ipalities in three counties in central Norway. The clinical presentation with oropharyngeal tularaemia and  cervical lymphadenopathy linked to the use of private  wells in the winter season makes contaminated water the most likely source of infection in this outbreak.  Detection of F. tularensis DNA by PCR analyses in some  of the wells supports this assumption for some of the  cases. Use of private wells is relatively common in  rural areas of Norway although exact data on such use  are not available.  The precise mechanism of contamination of the  wells with F. tularensis is as yet unknown. However,  November and December 2010 were unusually cold  months, while in January 2011 temperatures increased  leading to melting of snow and possible contamination  of private wells by surface water contaminated with  bacteria from rodent cadavers or rodent excreta. Since  the incubation period for tularaemia may be up to three  weeks, and time from symptoms until seroconversion  might be up to six weeks, more cases may follow.  Tularaemia has traditionally been called both lem- ming fever and hare plague and this clearly indicates  rodents and hares as transmitters of disease. Years  with a great increase in the rodent population are seen  with intervals of about three to four years [11] and in  the summer and autumn of 2010, a high density of  lemmings could be observed in the southern and cen- tral parts of Norway. Simultaneously, the Norwegian  Veterinary Institute observed a wide geographical dis- tribution of fatal cases of tularaemia in the mountain  hare (Lepus timidus) in these regions [12]. The moun- tain hare is very susceptible to this infection and nor- mally dies from septicaemia within a few days after  exposure.  The use of small streams and private wells as a source  of drinking water and for other purposes in rural areas  of Norway is a matter of concern. In existing guidelines issued by the National Institute of Public Health the population is advised to boil drinking water and inspect the wells for dead rodents in case of suspected or confirmed cases of waterborne tularaemia. Every well owner should make the necessary effort to prevent small rodents from entering the well water by carefully covering every opening and plugging every small holes  where the rodents can enter. It is also important to  secure the well from contamination by surface water  after snow melting. In case of proven or suspected  contaminated wells, the water should be disinfected  before further use. However, this may not be feasible  for persons who use drinking water from a stream. The Norwegian Food Safety Authority has recently released information to the media and to the general public with  similar advice and information in relation to the current outbreak. The local health authority in each municipality is responsible for instituting infection control measures including advice to the public and investigations of the putative drinking water sources. References 1. World Health Organization (WHO) Epidemic and Pandemic Alert  and Response. WHO guidelines on tularaemia. Geneva:WHO;  2007. Available from: http://www.who.int/csr/resources/ publications/WHO_CDS_EPR_2007_7.pdf  2. Brantsaeter AB. Twenty-five years of tularaemia in Norway,  19782002. Abstract number: 10.1111/j.1198-743X.2004.902_ o142.x. European Society of Clinical Microbiology and  Infectious Diseases. 14th European Congress of Clinical  Microbiology and Infectious Diseases. Prague; 1-4 May 2004.  3. Trnvik A, Priebe HS, Grunow R. Tularaemia in Europe:  an epidemiological overview. Scand J Infect Dis.  2004;36(5):350-5.  4. Willke A, Meric M, Grunow R, Sayan M, Finke EJ, Splettstsser  W, et al. An outbreak of oropharyngeal tularaemia linked to  natural spring water. J Med Microbiol. 2009;58(Pt 1):112-6.  5. Rike HF, Vigerust A, Bergh K. Vannbrent utbrudd av tularemia  (harepest) i Midtre Gauldal. [A waterborne outbreak of  tularaemia in Midtre-Gauldal]. Norwegian Institute of Public  Health. 27 Oct 2003. Norwegian. Available from: http://www. fhi.no/eway/default.aspx?pid=233&trg=MainLeft_5669&MainL eft_5669=5544:27208::0:5667:1:::0:0  6. Brantsaeter AB, Krogh T, Radtke A, Nygard K.  Tularaemia outbreak in northern Norway. Euro Surveill.  2007;12(13):pii=3165. Available from: http://www. eurosurveillance.org/ViewArticle.aspx?ArticleId=3165  7.  Melien P, Holsdal RE. Tularemi i Meldal  en vanskelig  diagnose? [Tularaemia in Meldal- a difficult diagnosis?].  Norwegian Institute of Public Health. 18 Mar 2008. Norwegian.  Available from: http://www.fhi.no/eway/default.aspx?pid =233&trg=Area_5626&MainArea_5661=5619:0:15,4427:1: 0:0:::0:0&MainLeft_5619=5626:68396::1:5625:1:::0:0&Ar ea_5626=5544:68400::1:5628:1:::0:0  8. Bevanger L, Maeland JA, Naess AI. Competitive enzyme  immunoassay for antibodies to a 43,000-molecular-weight  Francisella tularensis outer membrane protein in the diagnosis  of tularemia. J Clin Microbiol. 1989;27(5):922-6.  9. Sjstedt A, Erikson U, Berglund L, Trnvik A. Detection of  Francisella tularensis in ulcers of patients with tularaemia by  PCR. J Clin Microbiol. 1997;35(5):1045-8.  10. Tomaso H, Scholz HC, Neubauer H, Al Dahouk S, Seibold E,  Landt O, et al. Real-time PCR using hybridization probes for  the rapid and specific identification of Francisella tularensis  subspecies tularensis. Mol Cell Probes. 2007;21(1):12-6.  11. Semb-Johaansson A, Ims RA. Smgnagerne [Rodents]. Semb- Johansson A, Frislid R, editors. Oslo;1990. 121-71. Norwegian.  12. Norwegian Veterinary Institute. Flere tilfeller av harepest i  Sr-Norge [Severeal cases of tularaemia in South-Norway].  Norwegian Veterinary Institute. 25 Nov 2010. Norwegian.  Available from: http://www.vetinst.no/index.php/nor/Nyheter/ Flere-tilfeller-av-harepest-i-Soer-Norge 

{'answer_start': [500], 'text': ['contamination of the wells  with infected rodents or rodent excreta']}