What is the type 3 scenario that worries the government so much?

“In Italy we have a type 3 scenario.” With these words, referred to during Question Time in the House today, the Prime Minister Giuseppe Conte defined the current epidemiological situation in which Italy finds itself. Infections continue to increase (today 24,991 new cases and 205 deaths) and the government runs to cover Dpcmbut what is the type 3 scenario?

Coronavirus, what is the type 3 scenario

The meaning of the term used by the Prime Minister is found in a study of Scientific Technical Committee entitled “ Prevention and response to COVID-19: evolution of the strategy and planning in the transition phase for the autumn-winter period ”, published at the beginning of October in the site of the Ministry of Health. The document, taking into account the references identified by the World Health Organization, hypothesized four possible scenarios for the evolution of the epidemic in Italy. The severity is in ascending order, so scenario 3, which is where we are at the moment, is the last stage before the worst scenario.

Conte announced that this scenario “ foresees the possibility of interrupting some particularly risky activities, even for hours, the possibility of staggered lessons for school, increased smart work to decongest transport ”, but these are just some of the planned measures for this scenario.

Coronavirus, the four scenarios of the pandemic

But let’s go step by step. Before delving into the Type 3 scenario, let’s go back a step and see what the four scenarios are according to the CTS document:

• SCENARIO 1: Localized transmission situation (outbreaks) substantially unchanged compared to the period July-August 2020, with regional Rt above the threshold for limited periods (less than 1 month) and low incidence, in the case that the transmissibility does not systematically increases at the beginning of the In autumn, schools have a modest impact on communicability and regional health systems can track and control new outbreaks, including school outbreaks.
• SCENARIO 2: Sustained and generalized transmissibility situation but manageable by the health system in the short-medium term, with regional values ​​of Rt in a systematic and significant way between Rt = 1 and Rt = 1.25 (that is, with estimates of the interval of 95% confidence – 95% CI – of Rt between 1 and 1.25), in the event that new outbreaks, including schoolchildren, cannot be fully traced, but still largely limit the potential transmission of SARS-CoV-2 with ordinary and extraordinary containment / mitigation measures. An epidemic with these characteristics of transmissibility could be characterized, in addition to the evident impossibility of containing all the outbreaks, by a constant increase in the incidence of cases (at least symptomatic; in fact it is possible that a reduction in the percentage of asymptomatic cases is observed identified versus the total given the impossibility of conducting epidemiological investigation for all new outbreaks) and the corresponding increase in rates of hospitalization and admissions to intensive care. However, the growth in the number of cases could be relatively slow, without causing a significant overload of care services for at least 2-4 months.
• SCENARIO 3: Sustained and generalized transmissibility situation with risks of maintaining the health system in the medium term, with regional values ​​of Rt in a systematic and significant way between Rt = 1.25 and Rt = 1.5 (that is, with estimates of CI 95% of Rt between 1, 25 and 1.5), and in which the transmission potential of SARS-CoV-2 can be limited only modestly with ordinary and extraordinary containment / mitigation measures. An epidemic with these characteristics of transmissibility is expected to be characterized by a faster growth in the incidence of cases than in scenario 2), the lack of monitoring of the transmission chains and the initial signs of overload of the care services after the increase in Cases of high clinical severity (with an increase in hospital bed occupancy rates – critical and non-critical area) attributable to a high or very high risk level based on the weekly monitoring system. The increase in the number of cases could cause an overload of care services in 2-3 months. However, it is important to note that if the epidemic spread mainly among the younger age groups, as observed in the July-August 2020 period, and it was possible to protect the most fragile categories (for example, the elderly), the time margin within which to intervene could be greater.
• SCENARIO 4: Uncontrolled transmissibility situation with criticality in the stability of the health system in the short term, with regional values ​​of Rt systematically and significantly higher than 1.5 (that is, with 95% CI estimates of Rt higher than 1.5). Even if an epidemic of these characteristics were to lead to more aggressive mitigation and containment measures in the affected territories, such a scenario could quickly lead to a high number of cases and clear signs of overload of the healthcare services, without the possibility of tracking the situation. origin of new cases. The growth in the number of cases could lead to an overload of care services in 1-1.5 months, unless the epidemic spreads predominantly among the younger age groups, as observed in the period July-August 2020 , and managed to protect the most fragile categories (for example, the elderly). In this regard, it should be noted that it seems highly unlikely to be able to protect the most fragile categories in the presence of an epidemic characterized by these transmissibility values.

Type 3 scenario: what it entails

According to the provisions of the Scientific Technical Committee, we are in scenario type 3, since currently “the regional values ​​of Rt mainly and significantly comprise between Rt = 1.25 and Rt = 1.5”. A scenario in which it is difficult to track infections, hospitals begin to have problems and that, in 2-3 months, would lead to an inevitable overload of healthcare services. A complex situation, in which the Regions experience different situations, some of them high risk: if this situation persists for three weeks, the document foresees stricter containment measures.

What is the weekly ranking

Another tool that is used during the Type 3 scenario is the weekly risk rating. It goes from ”low” a ”very high”, with the risk calculated taking into account the restrictive measures adopted. Obviously, the highest level is that which provides for movement limitation, return to confinement and large-scale smart work, but Italy is not currently in this situation. The current risk classification is not yet at alarm levels, but if the situation worsens in the coming weeks, according to the CTS document, it would be necessary to make new “difficult decisions”, such as closing schools and universities, limiting mobility in some areas and implement local restrictions in red areas. A scenario, type 4, that it would be better not to know.