Editorial

Three months after the first case of COVID-19 was detected in Mayotte, the epidemic continues. Following a lull during the second half of May, indicators have revealed a recent resurgence of the disease. These results should be interpreted with caution, given the broader context.

To describe and understand the dynamics of the epidemic, several surveillance systems have been implemented by Santé publique France (SpF) in collaboration with its partners. The data collected enable monitoring of the epidemic’s progression and assessment of its severity. Epidemiological analysis helps guide decision-makers in adapting the strategy to combat the epidemic.

As of June 10, 2020, 2,206 cases of COVID-19 had been confirmed by the CHM laboratory and the island’s private laboratory. These facilities can perform up to 200 tests per day when testing supplies are available. To date, more than 8,000 PCR tests have been conducted over three months, corresponding to 7,673 individuals tested. Since June 10, the private laboratory has been able to perform serological tests for the qualitative detection of IgG antibodies against SARS-CoV-2. To date, given the uncertainties surrounding the immunity conferred by infection, the use of serology remains limited to specific situations.

Currently, the COVID-19 testing strategy remains unchanged in Mayotte: any patient presenting with clinical symptoms suggestive of COVID-19 must undergo diagnostic testing. However, in recent weeks, case detection capabilities may have been compromised by changes in testing practices (epidemiological or clinical confirmation of cases, particularly for paucisymptomatic cases, and reduced mobile testing teams). Nevertheless, a resurgence of cases has been observed following the Eid celebrations and the reopening of businesses. Thus, it is likely that the scale of the current epidemic is underestimated.

Expanded testing operations are also being organized by the ARS and SpF as part of efforts to identify high-risk situations and clusters. These operations can influence the trajectory of the epidemic curve and epidemiological indicators. This is the case this week with the campaign conducted at the correctional facility, which altered the positivity rate, the sex ratio, and the average age of cases. This operation was initiated due to the specific epidemic risk within the prison setting. As a result, 204 cases were detected (inmates, staff), but the health impact of this cluster was limited given the youth of the prison population (average age of 26 among inmates) and their generally good health. The rate of asymptomatic infections was 56%, highlighting the proportion of patients who do not develop symptoms of the disease.

It is currently difficult to determine the proportion of asymptomatic COVID-19 patients (estimated between 20% and 40% according to various studies). The best way to gain a clearer picture of the epidemic’s dynamics is to facilitate access to testing for individuals meeting the criteria for testing. Ideally, and to ensure this visibility, all close contacts of a confirmed case should be screened. This would also help ensure better control of the epidemic’s spread.

Despite the rise in COVID-19 cases, each patient is still subject to a comprehensive investigation (medical-social assessment, tracing the source of infection, identifying vulnerable individuals) with the goal of breaking transmission chains. This is still carried out by SpF and the ARS until the new multi-level organizational structure is implemented.

In Mayotte, the severity of the epidemic appears to be relatively low (few cases admitted to intensive care and low mortality). This trend specific to the department can be explained by the youth of the population. However, although COVID-19 causes a mild form in the vast majority of cases, patient profiles likely to develop severe forms have been identified. The identified risk factors (cardiovascular diseases, diabetes) are particularly prevalent in Mayotte. A study aimed at describing the profile of patients hospitalized in medical wards has been initiated by infectious disease specialists and SpF. Furthermore, 8 cases of pediatric multisystem inflammatory syndrome have been recorded since the start of the epidemic. This phenomenon is also under surveillance.

Today, viral circulation continues, even as daily life resumes. Adhering to preventive measures remains a daily challenge for residents. Supporting the population remains essential to the process of lifting lockdown restrictions. Individual susceptibility and exposure to infection are two factors that can vary considerably from one individual or population group to another. This heterogeneity in viral transmission confirms the need to make mask-wearing universal to limit contagion. It also suggests dedicating concrete resources to prevent the emergence of outbreaks in situations conducive to close and prolonged contact (ceremonies, professional meetings, political gatherings, etc.), particularly in enclosed spaces.

Consequently, the primary focus of epidemiological surveillance is now the early detection of clusters to ensure the implementation of immediate control measures. To date, two outbreaks are still under investigation, and one cluster in a healthcare facility remains under surveillance.