Mauritius is famous for many things to many people: some knows us by our blue stamps, some by our idyllic vacation-island destination; others, for our malaria eradication efforts. The novel coronavirus has further increased our visibility by World Health Organisation (WHO) listing Mauritius as one of 13 African Nations with a high vulnerability for Covid-19 importation at the outset of the pandemic. Now, the management of the pandemic has earned us international accolades from BBC and WHO.

The BBC-TV recognized the efforts of Mauritius and rated us as one of two African countries with extensive testing for the virus. The Director General of WHO-Africa has praised our efforts for successfully quelling the pandemic. It is time to recognize what has been collectively achieved through the cooperation of the population and inputs and contributions of all stake-holders, including the media. We should pay tribute to all who have risked their lives to protect the nation and to take stocks of the perilous road ahead.

How are we faring in the Indian Ocean? 

To recap, we have registered 332 cases to-date, with 10 mortalities, a cure rate of 98% and registered zero incident cases over a period exceeding 14 days. The WHO model of SARS-CoV-2 transmission asserts pandemic initially starts as sporadic cases, illustrated by current situation in Seychelles and Madagascar, with 11 and 169 sporadic cases respectively. If containment measures are delayed, the sporadic cases progress to cluster of infection as seen in Reunion with clusters of 433 cases. Undoubtedly containment by contact tracing and case-isolation work best when the pandemic is at sporadic and cluster stages, as illustrated by Seychelles, Reunion and Madagascar islands.

If containment measures are delayed, the clusters progress to the next level and establish community-level transmission. Currently, WHO classifies the pandemic in Mauritius as community level transmission, which implies that we missed a window of opportunity to pre-emptively contain the pandemic at the sporadic and cluster stages. However, once this shortcoming was remedied by drastic lock down, it significantly reduced the incident cases to zero. It is interesting to speculate that our stage of pandemic may be one of determinants of mortality as we are the only island in the Indian Ocean to register COVID-19 mortality. The fact that we have achieved 96% cure rate suggests most of the cases are mild since it is generally believed that 80% of clinical cases are mild and require no medical treatment.

What does the surveillance data tell us?

I have analysed the secondary data of the Ministry to look for frequency and pattern in an effort to evaluate our performance. The daily cases are plotted to obtain an epidemic curve, shown in accompanying graph. We may conclude from the epidemic curve that confinement measures have significantly interrupted the chain of transmission. However, this conclusion is predicated on two assumptions: the surveillance system is complete and exhaustive and a valid test is used. But we know the surveillance system needs improvement because the epidemic curve shows an abrupt drop from 41 to 4 cases on April 10^th, a pattern that betrays inconsistencies: an efficient surveillance should have shown a gradual drop.

On the testing front, we have extensively expanded our capacity to test by PCR from an initial 300 tests to 25,000 samples, but we have partly undermined this effort by introducing an unvalidated rapid antigen test method which, WHO reservedly qualifies as “the use of these new point-of-care immunodiagnostic tests only in research settings. They should not be used in any other setting, including for clinical decision-making, until evidence supporting use for specific indications is available.” WHO further warns “half or more of COVID-19 infected patients might be missed by such tests” and “false-positive results – that is, a test showing that a person is infected when they are not”.

So, the validity of the 50,000 rapid tests carried so far remained to be established. Undoubtedly, countries are faced with the issue of large-scale testing and resort to rapid antigen-based testing as opposed to the gold standard test of PCR, that is resource intensive. However, PCR can also be modified to be less resource intensive by pooling several samples for testing.

The roadmap ahead

There are three epidemiological imperatives: 1) expansion of community-based surveillance, 2) use of validated laboratory tests and 3) maintenance of social distancing with all its associated precautions. The typical patterns of transmission of SARS-CoV-2 virus starts with an infected person contaminating health personnel or frontline worker, who in turns sets off a chain of transmission by infecting their families and eventually the whole community. We test to find out covert cases in the community, especially as a tool to monitor community-level transmission after lockdown is lifted, therefore we have to target our testing by a probability-based sampling and a validated laboratory method.

Our sampling strategy must move from convenience samples to random representative samples. Some 80% of symptomatic cases experience only mild flu like symptoms with no complications and may not seek medical care, thus escaping the surveillance net. This issue can be circumvented by regularly conducting random community surveillance and instituting event-based surveillance in public places.

Precautionary principles to save lives

Managing COVID-19 pandemic is a nightmare for governments round the world, who are experimenting with different control options. Policy makers have to navigate the perilous choice of protecting lives and preserving scare resources, often based on incomplete risk assessment. The biggest challenges to risk assessment centre around the hitherto unknown properties of the virus: the exact duration of virus shedding before and after appearance of symptoms as well as the proportions and roles of asymptomatic persons in fuelling the epidemics.

When Health Protection Agencies around the world, including Mauritius,  re-define the new norms of health agenda, they have implicitly or explicitly factored in the facts that; 1) the undauntable challenges of stamping out the virus once it has introduced in the community, 2) the probability of transmission per contact may be as high as 40%, 3) the limitations of the surveillance system in detecting all cases especially the asymptomatic ones, 4) the exceptional incubation periods of some persons exceeding 14 days, 5) the duration of infectivity symptomatic and asymptomatic cases, 6) the degree of herd immunity required to halt the pandemic, 7) the risk of a second or series of subsequent waves because the pandemic cannot be halted as long as there are susceptible persons and the virus lurking in the world, and 8) the fact that the virus, if not killed by disinfection, may survive in air for 3 hours, on plastic copper, stainless steel and cardboard surfaces for 3 days. So, to save lives governments err on the conservative sides of the precautionary principles in formulation of health policies.

A health policy in the making

When I first highlighted the gravity of COVID-19, the role of asymptomatic and the need for testing before declaring zero cases, my concerns were branded as heresy in some circle and my proposal for wearing mask was frowned upon for fear of scaring away tourists or local population. But my proposal raised public awareness and eventually became the cornerstone of national policy. Health policy formulation starts with public agenda setting, and today it is reassuring to attest that many of my initial alerts and recommendations have been incorporated in our health policy to protect the health of the whole nation.

We have to continue our collective actions in building a resilient health system that responds to the needs of the population in real time, and to integrate global knowledge into our policy decision. Olympic Gold medallists know that they have to invest sustained efforts or even surpass their previous efforts to maintain their prized medals, else they fall below the bench-mark.