In our , we mentioned that Professor Philippe Sansonetti, Chair of Microbiology and Infectious Diseases at the Collège de France, and Medical Director of the Institut Pasteur from 1995 to 2000, outlined in a lecture how each of us can play a part to flatten the curve of this pandemic. Entitled « Covid-19 or the chronicle of an announced emergence », the lecture was delivered at the Collège de France on 16 March 2020.
A trained microbiologist, Professor Philippe Sansonetti is the valued opinion on the pathogenesis of Shigella, a bacterium causing severe diarrhea. His work spans a large set of disciplines in biology and medicine and ranges from molecular genetics, to cell biology, immunology and the development of vaccines against dysentery.
In the second part of Prof Sansonetti’s lecture, « Covid-19 or the chronicle of an announced emergence 2 » on 14 April 2020, he spells out the perils of easing lockdown measures prematurely and lays down the necessary conditions for the lifting of a lockdown – which will not put an end to social distancing measures.
The initial strategies
To combat the Covid pandemic, countries deployed the initial strategy of social distancing measures and encouraged their populations to observe proper hand hygiene. It soon became apparent that these actions alone were insufficient weapons in this battle. Infections continued to rise exponentially, as seen in France, Spain, Italy and the United Kingdom, threatening to saturate intensive care resources.
There were then two solutions: the bet on herd immunity and social distancing.
- Herd immunity
This method involved a change-nothing strategy. The idea was to wait until the prevalence of the infection in the population reached a sufficiently high percentage (60%) of immunised individuals to prevent the virus from circulating further for lack of finding enough people with no immunity.
This was based on the premise that the disease would confer a strong protective immunity, which has not yet been proven for Covid. This option was not viable, given the number of seriously ill patients that would be generated in a very time. In addition, the virus is very highly contagious, with people transmitting it despite still being asymptomatic or starting to experience minor symptoms. Clearly, the real number of carriers is higher than that reported by hospitals. The history of epidemics underscores the importance of being fully able to identify patients, including healthy carriers, and initiate effective control of the pathogenic spread. Medical staff, especially those on the frontline, too are often victims of the very disease they treat. Hence the need to maintain sufficient stocks of suitable protective equipment.
- Social Distancing and Lockdowns
The next weapon in the arsenal was social distancing measures leading to the closure of schools, public places and “non-essential” services and the lockdown of entire populations, with full awareness of the economic and social costs of this decision. The small success of these measures after four weeks gives a hint of the magnitude of the disaster that would have befallen had only the original social distancing measures been implemented.
Reasons for the initial failure of the social distancing measures in France
Understanding these reasons will be instrumental in defining the success of an exit from a lockdown. In truth, this cannot be achieved without continuing social distancing measures under the right conditions and with the commitment of all.
- The population did not take the crisis seriously
Many citizens, especially young adults who thought the disease affected mainly those over 65, were complacent about personal hygiene and social distancing measures. Another reason was the lack of public confidence in the scientific, medical and government authorities. When the measures taken to combat the A-H1N1 influenza virus in 2009 by the authorities proved to be more than what was necessary (given that the virus turned out to be relatively benign), public confidence was eroded.
- The lack of diagnostic tests (q-RT-PCR)
The lack of capacity resulted in the missed opportunity to adopt a broad–based testing to identify patients for isolation and to do contact tracing, at the moment when the epidemic was accelerating. This has allowed the exponential transmission of the virus to develop, with an R0 higher than that of the seasonal flu. Countries that have carried out these tests extensively, such as Korea, Taiwan, Singapore and even Germany show a better record, particularly in the absolute numbers of deaths.
- The shortage of masks
Personal hygiene measures were limited in their success due in part to a shortage of medical grade masks. Given the shortage, it was logical to reserve the stocks for healthcare personnel. The communication put out to the general public then was to discredit the use of masks, saying that these were ineffective, with experts divided on the subject. However, given the active circulation of the virus and the knowledge of its transmission by droplets and aerosols, a far better approach was to have encouraged the making of masks by households, even if these did not confer a 99% protection. In an epidemic, anything used to reduce transmission is good. Nonetheless, it had to be explained to the general population that the mask was to be used hand in hand with the other hygiene measures.
Examples of the Asian countries
Asian countries such as China, Singapore, Taiwan and South Korea, achieved early success through various policy controls : lockdowns and the early implementation of social distancing. This is seen in the intensive individual hygiene measures taken, including the use of masks by the general population, the extensive carrying out of diagnostic tests combined with the use of artificial intelligence to do contact tracing. Those at risk were isolated or quarantined, especially the elderly.
These countries are of course not immune to a resurgence of the virus as they likely did not, due to this initial success, achieve the prevalence of infections necessary to develop herd immunity. Singapore, considered a model early on the fight, has seen its number of cases, including deaths, soar in recent days and decided on 7 April 2020 to go into a lockdown.
Conditions for easing measures and the steps to be put in place even after these measures are lifted
The end of a lockdown does not signal the end of the epidemic. It will always be there, less virulent no doubt but always with the threat of a resurgence. While it would not be practical to wait for the discovery of a vaccine or an effective drug, several conditions must be met before measures may be eased.
1 – The easing of measures by zones
This is provided that the epidemiological data available indicates that the peak has passed or that the infection rate in these zones has not been increasing over several weeks. Diagnostic tests based on very broad, methodologically indisputable serological studies to determine the percentage of the population having been infected with SARS-CoV-2 via the presence of specific antibodies, in addition to molecular diagnostic tests done through q-RT-PCR need to be carried out.
It is clear that the date of the lifting of a lockdown will have to be decided on objective criteria. While there exist brilliant models of prediction through the integration of sophisticated and efficient mathematical algorithms, there are still grey areas in the SARS-CoV-2-human interaction which make such predictions difficult. Questions remain; do cured patients or those who are asymptomatic or showing mild symptoms have immunity, and for how long, what would it take to acquire an effective herd immunity and will vaccines confer sufficient protection. Further research is required to shed light on these obscure yet critical aspects of the disease.
Also to be weighed are the consequences of an easing if there are populations with subjects at higher risk of developing serious complications (older than 65, the immunocompromised, diabetics, the obese).
2 – Extensive and broad–based testing
This must be carried out in as broad a population base as possible on symptomatic, asymptomatic patients or those showing mild symptoms, with a particular attention on persons, professions and zones at risk, and isolating those who return positive, under conditions that remain challenging in their complexity.
Such an approach will naturally be associated with the search for the close contacts of these infected patients; the famous “contact tracing”. This has given rise to the perception of an intrusion into personal privacy. However, the public must be made aware of the importance of this action through transparent education and be encouraged to support it, playing an active role alongside healthcare personnel and the police after the lockdown is lifted.
Another resource to tap on is the scientific community. Aside from the minority working on Covid-19, the rest of the hundreds of thousands of scientists can support the war effort by converting their laboratories into diagnostic centres.
3 – Continued maintenance of social distancing measures and personal hygiene standards
This includes the wearing of masks, whether “professional” quality or homemade, in public gatherings, or public transport when economic activities restart.
4 – Limited inter-regional travel
With exceptions to be defined according to business requirements.
5 – Prohibition of gatherings
Gatherings must remain forbidden except for certain restricted exceptions such as funerals. Solutions must be found for practising social distancing when our economic and social life resumes (in offices, restaurants, schools etc.).
Relaxation of these measures may only happen if we have a real mapping of the evolution of the epidemic, and when the R0 is below 1 (below the epidemic threshold), pointing to the absence of a resurgence. Currently, this information is not known and SARS-CoV-2 can modify its behaviour at any time, in the good or bad sense, due to a mutation.
Perhaps the price we pay for this epidemic will be in exchange for herd immunity, admittedly insufficient, but which, combined with rigorous social distancing measures, will effectively block the circulation of the virus.