Unavoidable waves

The price for ensuring the nation’s health is eternal vigilance and patience.

Published : May 16, 2020 18:04 IST

Health-care workers on their way to conduct door-to-door check-ups at Mukund Nagar in Dharavi on May 15.

Health-care workers on their way to conduct door-to-door check-ups at Mukund Nagar in Dharavi on May 15.

As India passes through lockdown 3.0, with many other countries in the same path, there are questions from experts in disciplines ranging from medicine to sociology and politics whether this is the right approach to counter COVID-19. This is often followed by the queries about a possible “perpetual lockdown” or an “extended, long-term lockdown”. A colleague from Hokkaido Prefecture, Japan, who spoke to one of the authors (SH) recently, said: “Where did we go wrong? Should we have remained in perpetual lockdown?”

Unfortunately, these are the realities of a pandemic. It comes unannounced, with ever new transmission dynamics, and hits susceptible groups of populations against a backdrop of a overconfident human race with its technological advancements and artificially evolved national and international conceptual and geographical boundaries. Even before the first horrific phase of the COVID-19 pandemic has run its course globally, there are worries about the second and multiple waves of the disease. These may be worse than the first, killing tens of thousands of people who did such a good job of maintaining social isolation and who remain virgin ground for the virus. Or, there may be a mere swell, with so many people having been infected without symptoms that levels of immunity are higher than is realised. We do not know, and so many crucial pieces of information remain missing.

Besides, the reality is that COVID-19 has not even completed its first peak in all countries, which leads to worries that it may be premature to talk about “repeat waves”. No doubt that until there is a vaccine, or at least a cure (a longer route than a vaccine), there will be no peace of mind. In the current interconnected global economy there is no realistic solution to avoid repeat waves. If there were, Singapore and Japan would not have gone for delayed lockdowns—a final testament to defeat in the face of COVID-19.

There are many questions that need to be answered. Are those who have been infected once with the virus now immune to it? Herd immunity normally requires that at least 85 to 95 per cent of the people should become immune to the virus in order to avoid a future outbreak. Korea has reported that 2 to 3 per cent of survivors tested positive again. Second, if at all people do become immune, how long does the immunity last? We do not know; after all we know COVID-19 for only four months. Third, does the virus have a seasonal pattern such as influenza and common cold do, peaking during cooler months and falling during the warmer ones? Probably not, as it has a footing in tropical and arid countries already.

Fourth, what is the actual number of days when viral shedding continues without symptoms, before the symptoms manifest themselves in an infected person and after the symptoms appear? Answering these questions will take time and will require following up on exposed persons. The current assessment of the number of days of viral shedding is as good as the data that are available.

Finally, no one has so far assessed the extent of community prevalence. This requires population-based surveillance systems, where samples of people are tested randomly to avoid bias. A study reported recently from San Francisco showed that 2 per cent of the population in one county reported several fold higher numbers of infections than what had been tested and reported. A newly published research based on mathematical modelling confirms a generally held consensus that China’s aggressive control measures halted the first wave of COVID-19 in areas outside Hubei province, the epicentre of the epidemic. The study estimates that in regions outside Hubei, the instantaneous reproductive number of COVID-19—the average number of cases generated by a single infected individual during the outbreak—fell substantially after lockdown measures were introduced on January 23 and has remained below 1 since then, suggesting that the epidemic shifted from one that was expanding rapidly to one that is slowly shrinking. (The higher the reproductive number, the more transmissible the virus is and the higher the risk for rapid spread. When the reproductive number falls below one, the epidemic is likely to die out.)

The common-sense view, confirmed through mathematical models that simulate the impact of relaxing current control measures, is that premature lifting of these interventions will likely lead to transmissibility exceeding 1 again (meaning each infected person transmitting infection to more than one person), resulting in a second wave of infection. The remarkable difference in the case fatality rate between these locations and Wuhan, capital of Hubei, might be attributed to the difference in the degrees of health-care capacity. Therefore, consideration should be given to the variations in health-care capacity—age structure (more elderly), and the presence of people with other diseases (diabetes, hypertension, tuberculosis)— when implementing interventions. Whether infections dominate or not varies extensively between countries and within countries in slums or geographic areas where people with one of these risk factors live.

No doubt, initial control measures appear to have reduced the number of infections to very low levels, without herd immunity against COVID-19. However, cases could easily resurge as businesses, factory operations and schools gradually resume and increase social mixing, particularly given the increasing risk of imported cases from overseas as COVID-19 continues to spread globally. Professor Gabriel M. Leung from the University of Hong Kong said: “Even in the most prosperous and well-resourced mega cities like Beijing and Shanghai, health-care resources are finite, and services will struggle with a sudden increase in demand.”

It is not the duration a country has been in lockdown that determines the end of a first wave. Rather, it is the following criteria that determine if success has been achieved.

Conditions to be met for relaxation of mitigation measures:

* Assure cases are no longer spreading widely. This can be achieved through population-based sero-epidemiological studies, but they are expensive and time-consuming. Therefore, in the interim, track the COVID-19 epidemic curve with saturated testing (proposed ideal number of tests based on several mathematical models call for a moving average of 100-152 tests per 1,00,000 population per day). Demonstrate decreasing case rates through test positivity (beginning with below 10 per cent and declining towards zero) and decreasing trends in syndromic cases, and fewer unlinked cases over a 14-day period indicates response. Fourteen days of absence of new cases may signal transition to limited relaxation of mitigation measures.

* Assure reactivation capacity. The above listed maximum range of case finding capacity through testing and contact testing is sustainable and ready for activation as soon as cases emerge.

* Verified resilience of the entire health-care system. This includes the ability to protect safety of front-line workers in critical or high-risk settings with adequate personal protection equipment, adequacy of surge capacity for estimated caseload in a pandemic situation, including critical medical equipment intensive care capacity.

* Special measures to protect medically vulnerable persons. Such measures will be required at all times until the pandemic is declared over, or adequate vaccination coverage is achieved. Continuation of mitigation measures for vulnerable populations is irrespective of relaxation of shelter-in-place for other population groups, or cessation of restriction on economic, social, and community activities.

Averting resurgence (waves):

* This is possible only if the first wave is successfully curbed in the ways described above. Otherwise, it is not resurgence but an escalation of the first wave.

* Identify and mitigate resurgence risk. Assess, categorise and grade activities with the highest potential for disease introduction (eg: transport link with countries or regions in active disease transmission, high-volume events) and develop tailored public health strategies to avert them. Measures include cancellation of select routes, continuous disinfection in high traffic areas, provision for hand hygiene and physical distancing, sustained use of face coverings, and temperature and symptom monitoring.

* Transparent communication is crucial. The target population should be continually updated with information about sporadic detection of cases and the epidemic situation in other regions or countries with potential epidemiologic link.

The price for ensuring the nation’s health is eternal vigilance and patience.

We need patience with lockdown and vigilance for the enemy, not a reactive ease of lockdown based on a number of days. COVID-19 with its long incubation period and asymptomatic spreading, a case anywhere (in India, or the world), is potentially a case everywhere (in India or the world). It is possible to go from 100 known cases a week to 65,000 a few weeks later.

There is a cautionary tale from the 2003 outbreak of SARS in Toronto, which infected 375 people and killed 44. The city took extensive precautions beginning in March but lifted them in May when the outbreak appeared to be over. It was not. “Toronto took the brakes off. They had a flare, and it took them weeks to get it back under control,” says William Hanage of the Harvard School of Public Health.

Until a vaccine is available and can be distributed throughout the world, and without a worldwide “all hands-on deck” approach that will collectively and consistently track and contain each sporadic unlinked case of COVID-19, outbreaks are unavoidable. As the Dalai Lama says, our frustrations are due to our expectations. So, let us move knowing what the facts are.

Shahul Hameed, MD, M.Sc, Ph.D, is with the University of Sciences, Techniques, and Technology, Bamako, Mali, and Dr N.M. Mujeeb Rahman is with MES Medical College, Malaparamba, Kerala.

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