Researchers at the UPV/EHU and the Biodonostia Institute of Healthcare Research have analysed the epidemiology of rotavirus infection in Gipuzkoa, the impact of the illness, and the genotypes circulating between 1995 and 2015, and have provided information about this virus, which continues to be the main cause of severe, acute gastroenteritis in infants and young children.

"Tt is an illness that has been little studied in terms of its epidemiological characteristics, in other words, seasonality, distribution by age and incidence, and genotypes in circulation. That is why this work is providing fresh data that may be important for the health authorities when it comes to making decisions in the matter of healthcare, such as the deployment or otherwise of the vaccination against the rotavirus", said Ainara Arana, author of the research conducted at the UPV/EHU and at Biodonostia.

The study concluded that even though the impact of rotavirus infections has lessened throughout the monitoring period, it remains significant: the rotavirus has been the first cause of hospitalisation due to acute gastroenteritis in children under the age of five. During the twenty years covered by the research a reduction has been seen not only in outpatient samples but also in the number of cases admitted to hospital as a result of rotavirus gastroenteritis. "This fact could be linked to the better management of infant diarrhoeas in the family environment, improvements in healthcare, and increased use of oral rehydration solutions that provide fluids and salts to reduce the risk of dehydration, above all in very small children. So many of the cases are treated at home by parents and are not referred to hospital".

On the other hand, during the last five years of the study a delay in the onset of epidemics has been noticed. "In countries in the south of Europe (Spain, Italy, etc.) the epidemics usually start around November and in countries located further north, such as the United Kingdom, they start later on, around January. Yet we have seen that in our area from 2011 onwards the onset of the epidemic has been delayed until January or even February, and tends to be on a par with those of countries in Northern Europe," added Arana. With respect to the causes of this shift, "it could be due to climate change or to the fact that some of the nearby European countries have greater vaccination coverage, although these are mere hypotheses". With respect to the genotypes circulating in Gipuzkoa, "their distribution is fairly similar to that observed in Europe: G1 is the most frequent genotype, followed by the emerging G9 and G12 genotypes that are playing an increasingly significant role. During the last five years studied, G12 is even more prevalent than G1". However, the study highlighted the occurrence of infections by rare genotypes of animal origin (e.g. sheep) and the frequent circulation of viruses of various, distant geographical origins (Asia, Australia, etc.) and even of recombined viruses. The author of the study stresses the importance of "monitoring the strains circulating in our area to find out whether the vaccinations existing on the market continue to be effective since new genotypes could emerge and would make the modification of the composition of the current vaccines advisable".

Rotavirus reinfections account for just over 1% of the cases requiring medical assistance. "That does not mean that there have hardly been any reinfections, but that they did not need to go to the doctor". The study shows that most of the reinfections are caused by genotypes that are different from the one that caused the first infection, in other words, "if a child is infected by one type of virus, it is more probable that he/she will be reinfected by another type of virus that is different from the one that caused the first infection," added Ainara Arana.