Adrian Hugo Aginagalde
Spokesperson of the Spanish Society of Preventive Medicine, Public Health and Health Management (SEMPSPGS), Head of Service of the Epidemiological Surveillance and Health Information Unit of Gipuzkoa and, previously, Head of Service of the Population Screening Programmes Unit at the Ministry of Health
The change in the epidemiological surveillance model is conditioned by greater transmissibility and a lower hospitalisation and case fatality rate.
An attempt is made to address the intrinsic difficulty of respiratory infections, which is to try to carry out universal surveillance (of all cases) through diagnostic confirmation tests; something that has not been achieved in respiratory syncytial virus (RSV) or influenza (influenzavirus).
To this end, a sentinel (sample) model of mild and severe cases is established, combined with syndromic surveillance (of symptomatic cases) and virological surveillance (variants) and supported by additional tools (monitoring of temporary disabilities and wastewater).
The challenge is to design a transition between the two models, something that has not been done before, and with a disease of pandemic magnitude, with a much greater healthcare impact than other acute respiratory infections and the capacity to generate between two and three acceleration phases per year. Given this gap in knowledge and models of how to monitor in order to be able to react when necessary, the strategy makes a transition to surveillance of mild cases through medical record codes and of severe and vulnerable cases with a higher risk of hospitalisation. The aim is to be able to anticipate with sufficient accuracy sudden increases in the pressure of care.
At the same time, given the very high transmissibility of Omicron, which prevents the identification of contacts (the programmes collapsed in December) and concentrates its transmission in the days prior to the onset of symptoms, it is time to reconsider control measures such as isolation due to loss of effectiveness. It was an extraordinary measure, not widely applied with such a prevalent disease, never before used in an acute respiratory infection and which, in the absence of quarantines, due to the transmission of asymptomatic people, had limited effectiveness and important consequences.