Rotavirus and norovirus infections pose an important public health problem in Lithuania. The incidence increased from 0.2 cases per 100,000 population in 1994 to 88.4/100,000 in 2009. Rotavirus and norovirus infections made up 23.1% and 2.3 % of cases, respectively. Epidemiological investigations of sporadic and clustered cases show that most patients were infected in their home environment (72.1 %). Rotavirus infection predominated among infants and young children under the age of three years. Infection spreads primarily via food when food preparation safety is not followed (1).
Rotaviruses are ubiquitous: worldwide 95 % of children are infected by the age of 3 to 5 years. Infection can also affect elderly people and adults with a weak immune system. The severe form of the disease seen in primary cases affects infants and children between 3-35 months. Older children and adults may be infected repeatedly but with less severe forms of disease with or without clinical symptoms. Rotavirus and norovirus are viral infections with a faecal-oral route of transmission. The main risk factor is contaminated hands. The virus can survive for long time and can be spread by a variety of objects that children put in their mouths. The infection can be spread via food when food preparation safety is not followed. The virus spreads among children in groups, e.g. kindergartens, and adults are infected by their children (2). The most frequent manifestation of viral intestinal infection is vomiting, watery stools and fever (3).
Globally, viral intestinal infections cause approximately 35-50 % of diarrhoea cases among children. During a 6-year period the incidence of rotavirus infection in the Baltic countries (Estonia, Latvia, and Lithuania) were similar. The peak of rotavirus infection in the Baltic countries was observed in 2006: 115.6 cases per 100,000 population in Latvia, 100.6 cases per 100,000 in Estonia, and 143.7 cases per 100,000 in Lithuania. The incidence of rotavirus infection was lower in Lithuania (82.4 cases per 100,000 population) than in Latvia (140.3 cases per 100,000 population) and Estonia (118.1 cases per 100 000 population) in 2009 (Fig. 1) (4).
The objective of this study was to provide an overview of the current epidemiological situation and trends for rotavirus and norovirus infection in Lithuania.
Fig. 1. Incidence of rotavirus infections in the Baltic countries, 2004 - 2009
Materials and Methods
Laboratory-confirmed rotavirus infection cases have been notifiable since 1994 and norovirus infection since 2005 in Lithuania.
According to the Lithuanian communicable diseases reporting law, it is mandatory to report viral intestinal infection cases. Viral intestinal infection cases are reported by any health care institution that send information to the territorial Public Health Centre. The Centre for Communicable Diseases and AIDS receives this information from all territorial Public Health Centres via a computerised surveillance system. The Centre for Communicable Diseases and AIDS produces a national report and review of all notifiable communicable diseases.
Surveillance data on rotavirus and norovirus infections from 1994 to 2009 were analysed using Microsoft Excel program.
In 2009, 3304 cases of specified viral intestinal infections were notified in Lithuania, including 2782 rotavirus enteritis cases and 522 norovirus infection cases, as well as 3231 viral intestinal cases of unknown aetiology. The rotavirus enteritis trend rose significantly during 1994 to 2009 with a peak of 144.2 cases per 100,000 population in 2006. Rotavirus infection incidence decreased by 12.7 % from 2008 to 2009. (Fig. 2).
Fig. 2. The incidence of rotavirus enteritis in Lithuania, 1994 – 2009
Epidemiological surveillance of norovirus infection was started in 2005. The number of norovirus cases increased from 190 to 796 and then dropped to 522 cases in 2006, 2008 and 2009, respectively. Reported cases increased due to the availability of routine diagnostic methods in hospitals and public health care facilities. The incidence fell to 26.4%, from 21.5 to 15.8 cases per 100,000 population in 2008 and 2009, respectively.
Viral intestinal infections accounted for 37.3% of all intestinal infections in 2009. The percentage of viral infections among all intestinal infections increased from 18% in 2001 to 37.3% in 2009.
Notification of viral intestinal infections of unknown aetiology started in 1998. The morbidity trend of viral intestinal infections of unknown aetiology increased during 1998 – 2009. Over the last 5 years, the incidence increased from 16.5 to 98 cases per 100,000 population in 2004 and 2009, respectively. The incidence increased by 50.8 % from 2008 to 2009 (Fig. 3).
Fig. 3. The incidence of viral intestinal infections of unknown aetiology in Lithuania, 1998 – 2009
Until 2008, the incidence of rotavirus gastroenteritis among the urban population was nearly two times higher than among the rural population. In contrast, the incidence of rotavirus gastroenteritis in the urban population dropped by 21.3 %, from 121.1 to 95.3 cases per 100,000 population in 2008 and 2009, respectively. The incidence in rural population dropped by 8.8 %, from 63.8 to 58.2 cases per 100,000 population in 2008 and 2009, respectively.
Rotavirus infection predominated among infants and young children. As in every preceding year, the highest incidence of rotavirus enteritis in 2009 was among children less than 3 years of age (1601.2 cases per 100,000 children population). The incidence of norovirus and viral intestinal infections of unknown aetiology were also high among children under the age of 3 years. The incidence of viral intestinal infections was 6 times lower among 4-6 years old children and was similar among adults (18 – 65 years of age and older), under 23.3 cases per 100,000 population (Fig. 4).
Fig. 4. Incidence of viral intestinal infections by age groups in Lithuania, 2009
The epidemiological morbidity characteristics (seasonality, distribution by age groups) of rotavirus, norovirus and viral intestinal infections of unknown aetiology were very similar. Therefore we could assume that some rotavirus and norovirus infections were among the group of viral intestinal infections of unknown aetiology and were not specifically diagnosed. As a result, the actual incidence of these infections could be higher.
Viral intestinal infections have been reported from the majority of Lithuanian administrative units. The incidence of rotavirus enteritis varied between regions in Lithuania during 2009. The highest incidence of rotavirus enteritis was in Panevezys (143.3/100,000), Vilnius (141.7/100,000) and Silute (134.4/100,000). The incidence was lower in other regions (Fig. 5).
Fig. 5. The incidence of rotavirus enteritis in Lithuania by region, 2009
The reported incidence of norovirus infection reflects the capacity of diagnostic laboratories. Most cases of norovirus infection were diagnosed in Vilnius (47.9 /100,000), Kaunas (38.6/100,000) and Trakai (23.1/100,000) regions. The national incidence was 15.4 per 100,000 population. Sporadic cases of norovirus infection have been detected in Alytus, Siauliai and Telsiai regions (Fig. 6).
Fig. 6. The incidence of norovirus infection in Lithuania by region, 2009
The lowest number of rotavirus cases was registered in September (an average of 1.5 cases per day) while the highest number of cases was registered in March (16.7 cases per day). Most cases of rotavirus infection were reported between January and May. Rotavirus enteritis morbidity was lowest between June and December, less than the average daily rate. The highest incidence of viral intestinal infection of unknown aetiology was observed in November (an average of 12.3 cases per day) and the lowest incidence was in July (4.2 cases per day). The increased number of rota- and norovirus infections was observed during the winter to spring months. The number of overall viral intestinal infections was lowest during the summer (Fig. 7).
Fig. 7. Viral intestinal infections in Lithuania by month, 2009
According to the data of the Public Health Centers in Lithuania during 2009, 6.342 (97.4%) infections were notified as sporadic cases, 130 (2%) were reported as clusters of 2 cases and 40 (0.6%) as clusters with 3 or more cases. The majority (72.1%) of rotavirus infections occurred in home environment and for 19.8% place of infection was unknown. Some cases were detected in health care facilities and sanatoriums (2.9%), in childcare facilities (1.7 %), others (2.7 %).
During 2009, a total of 45 outbreaks of diarrhoea of viral aetiology were recorded in Lithuania; 40 rotavirus, 4 norovirus and 1 adenovirus. The majority of the outbreaks of viral aetiology (77.8%) occurred in families and 22.2% in children educational institutions. A total of 112 persons were infected in outbreaks and 106 (94.6%) were hospitalized.
An increased incidence of rotavirus infection and viral intestinal infections of unknown aetiology was observed during 1994 to 2009 in Lithuania. This can be in part explained by an increased laboratory capacity to diagnose these infections. Some cases were not laboratory-confirmed due to various factors including delay in sample delivery and that the samples had not been tested for rotavirus or norovirus infections. This may contribute to an increase in the reported incidence of viral intestinal of unknown aetiology infections.
Since 2004 the epidemic situation has been unstable in Lithuania and the incidence of rotavirus enteritis ranged from 66 cases per 100,000 population in 2004 to 88.4 cases per 100,000 population in 2009. The incidence in Latvia and Estonia was similar during the last 6 years. The trend of rotavirus infection in Lithuania was also similar with Finland, but more cases were detected annually in Lithuania during 2004 to 2009 (Fig. 8).
Fig. 8. Incidence of rotavirus infections in Finland and Lithuania, 2004 – 2009 (Source: EpiNorthData)
Rotavirus infection incidence decreased by 12.7 % between 2008 and 2009 in Lithuania. The highest incidence of rotavirus infection was recorded among children less than 3 years of age. Rotavirus infections can be prevented by vaccination. Today the rotavirus vaccine is not included in the national vaccination schedule for children but the vaccine is commercially available. The inclusion of the rotavirus vaccine in the schedule is currently under discussion in Lithuania.
The number of norovirus cases increased between 2006 and 2009 in Lithuania. Reported cases increased due to availability of routine diagnostic methods in hospitals and public health care facilities. The incidence dropped by 26.4% from 2008 to 2009 possibly because some cases were not tested for noroviruses and were reported as viral intestinal infections of unknown aetiology.
- Lithuanian Centre for Communicable Disease and AIDS. Statistical report form N 4 Morbidity of infectious diseases. [In Lithuanian]. Available from: http://www.ulac.lt/index.php?pl=19&ppl=9#metines
- Zagrebnevienė G. Rotavirusinis enteritas. Vilnius. Available from: http://www.ulac.lt/uligos.php?pl=20&ppl=59
- Bulonava. I., Titova. L., Samodova. O. Bulanova I.A., Titova L.V., Samodova O.V., Feklisova L.V. Rota- and norovirus infections among young children in Arkhangelsk oblast. EpiNorth. 2009;10(1): 6-12.
- EpiNorth, EpiNorth Data. Available from: http://www.epinorth.org/eway/default.aspx?pid=230&trg=Area_5279&MainArea_5260=5279:0:15,2937:1:0:0:::0:0&Area_5279=5291:44530::1:5290:1:::0:0&diseaseid=29