The infectious disease ‘outbreaks’ or ‘epidemics’ or ‘pandemics’ share a fate — there is a day when the majority of them run their course and fade away. However, a small proportion (of epidemics or pandemics) transitions to the stage of endemicity, i.e., a level of transmission which is not considered to be a major concern by the public or health authorities. It has been 29 months since COVID-19 was declared a pandemic. However, new COVID-19 cases are still continuing to be reported from different parts of the world, including India, on a regular basis. In fact, the numbers of daily new COVID-19 cases in many countries are more than what had been reported at the peak of the national waves in those countries before the emergence of Omicron as a variant of concern. However, the severity of COVID-19 infections is low and the burden of health services due to intensive care unit and hospital admission even lower. COVID-19 vaccination coverage is increasing and, in many countries, COVID-19 related restrictions have either been removed completely or relaxed to a large extent.
After the third wave in January 2022, India saw the lowest number of daily new COVID-19 cases in March and April this year. However, since then, daily cases have spiked to around 18,000 a day. In fact, in the last two months every rise and fall in daily cases in India revives the discussion on whether COVID-19 continues to remain pandemic or has become endemic. Yet, consensus is missing. Part of the reason is that the discourse is dominated by opinion and there has been insufficient attention on an objective assessment of what constitutes the endemic stage or endemicity.
An important point to remember is that the terms, outbreaks, epidemics, and pandemics reflect only the geographical spread. Outbreaks are a localised spread while an epidemic is when a disease affects a large geographical area within a country or a few countries. A pandemic is when multiple countries in different regions of the world are affected. The severity of the disease has no or very limited linkage with this classification and a disease could be mild; but if it is widespread, it could be termed a pandemic. COVID-19 began as an outbreak in China, became epidemic afterwards when more countries were affected, and then, finally, was declared a pandemic on March 11, 2020. It was not linked to the severity of disease. Severe Acute Respiratory Syndrome (SARS), in 2002-04, was a very serious disease, with one in 10 people who were affected dying; it was not declared a pandemic because severity does not determine this classification.
Here to stay
New diseases usually do not disappear completely. Chikungunya, dengue and many respiratory viruses usually stay within populations once they enter a population. Twenty-nine months into the pandemic, there is consensus that SARS-CoV-2 will stay with humanity for long, possibly for years and even decades. Cases are being reported from all countries and parts of the world and are likely to be reported in the time ahead. In this situation, it is important to ask how diseases transition from epidemic or pandemic to the endemic state.
We usually go back to history to get such answers. However, in the case of the COVID-19 pandemic, historical references are not very useful. The end points of the pandemics prior to the 18th century were determined retrospectively, when it was relatively easy to conclude a defined year. Then, the infections and cases in three major influenza pandemics in the 20th century (1918-20, 1957 and 1967-68) were identified based on symptoms; laboratory testing was not available for the pandemic in 1918-20 and was very limited in subsequent ones. In fact, in the 1918-20 flu pandemic, even the virus was not identified (it was first identified in 1933). If those clinical criteria of yesteryears are applied in ongoing COVID-19 cases which are now either mild and/or asymptomatic (thanks to vaccination and natural infection), one can conclude that the COVID-19 epidemic is over in many countries.
One of the ways to differentiate between ‘pandemic’ and ‘endemic’ is the ‘socio-economic’ impact. Pandemics are not merely health events but also encompass the social and economic implications of infections and diseases. For nearly two years, a large number of SARS-CoV-2 infections were happening in a short period of time — by a novel virus in a population which was completely immunologically naive — illnesses required hospitalisation and health facilities were overwhelmed. The infections, illnesses and hospitalisations understandably resulted in fear, panic and economic and social disruption. The interventions to halt the transmission of SARS-CoV-2, i.e., lockdowns, quarantines, national and international travel bans and school closure were equally unprecedented. There was a loss for many in terms of their sources of income after the ensuing social disruption and economic slowdown. Clearly, the impact was not restricted to those who tested COVID-19 positive; it has affected everyone and every member of society.
The risk of infection and disease under COVID-19, till early 2022, was unknown, and the outcome unpredictable. Two and half years into the pandemic — the risk of getting COVID-19 continues and will always be greater than zero, for long. However, there is better understanding now of who will get severe diseases. The risk of the social and economic impacts due to COVID-19 is minimal and close to zero. In such a backdrop, it is fair to conclude that while the health challenges of SARS-CoV-2 remain, the socio-economic impact is blunted. It is a good starting point to believe that the COVID-19 pandemic in India has moved to its endemic stage. However, that is not the same as saying that the pandemic is over. In epidemiology and public health, context (local setting, infection rate and vaccine coverage) determines the disease spread. Therefore, in the ongoing COVID-19 pandemic, every country would reach an endemic stage at different points of time. Countries that had higher vaccination coverage and higher natural infection (such as India) are likely to reach this stage early. Countries with low natural infection and vaccination coverage (as in Africa) would reach an endemic stage a little later.
A disease perspective
There is another dimension to the pandemic and endemic debate. Since pandemics have a social impact, the decision on when a country has reached an endemic stage is also determined by societal perspective of ‘the acceptable risk’. There are a number of countries across the world where societies have returned to ‘normalcy mode’ even though the per million daily cases in many settings are higher than cases at the peak of earlier waves. The United States has returned to a ‘no mandatory COVID-19 test’ for inbound passengers. In Europe, many countries are back to full normalcy.
Here is another example. HIV/AIDS was an epidemic in the mid-1990s. Now, HIV/AIDS cases are reported regularly but it is endemic because all societies/countries have agreed to it being an acceptable risk. Let us examine the data angle as well. In June-July 2022, around 30 deaths are being reported every day on average in people who tested COVID-19 (but did not necessarily die due to COVID-19). These numbers need to be seen in perspective. In India, an estimated 26,000 to 27,000 people die every day due to a variety of reasons which includes even old age. These daily deaths include 120 deaths every day due to pregnancy-related causes; 350 to 600 deaths in road accidents; 1,400 attributed to tuberculosis; around 2,000 deaths in children younger than five years due to different reasons, and 4,000 deaths every day attributed to tobacco and other related causes. Every effort should be made to avoid any death that is preventable. No society should be overly fixated over only one disease or health challenges. Clearly, COVID-19 is one of the many challenges and cannot continue to be the top and the only health priority.
The ongoing COVID-19 pandemic at the global level does not mean every country needs to have similar interventions in its response. India, arguably, has reached a stage where COVID-19 can be considered to be in its endemic stage. It is time to deal with the COVID-19 just like any other health condition and integrate COVID-19 interventions in general health services. It is time people do a self-assessment of their COVID-19 risk and undertake voluntary precautionary measures. COVID-19 vaccination should become part of the routine immunisation programme. There are other health challenges that are waiting to be tackled.
Dr. Chandrakant Lahariya is a primary-care physician, infectious diseases specialist and vaccines expert. He tweets at @DrLahariya