With multiple foes.
Plan, strengthen and guard yourself,
And your foe’s hopes will collapse”. (Thiruvalluvar: The Kural)
“It is within the power of man to eradicate infection from the earth.” This quote is ascribed to Louis Pasteur, well-known for discovery of evidence for the germ theory of disease and for the principles of vaccination. More than a century later and much before the outbreak of coronavirus disease (COVID-19), events in the recent past two decades had exposed the impulsiveness of the belief that we have won the war against microbes. Even as the 20th century drew to a close, we had to deal with at least a dozen new diseases such as AIDS, Legionnaires’ disease, and Hantavirus lung infection, in addition to resurging traditional diseases such as malaria and tuberculosis that had appeared to be on their way out. The reality is that infectious diseases remain a leading cause of illness and death world-wide. Clearly, the age-old battle of humans against microbes is not yet over. Indeed, it is not yet time to close the book on infectious diseases.
The current attack by corona virus has till date, left more than 12.5 lakhs people wounded and deaths exceed 68000. Hopefully, COVID-19 would be “less dangerous than the seasonal flu” as Professor Yoram Lass has noted and “is only an epidemic of mass panic” as Professor Peter Gotzsche wrote in a blog. Nevertheless, given the serious setback in our war on infectious diseases, it is pertinent that those of us who are not in the front line of the war ponder over developing back room strategies. This would involve combing records of past wars and strategies that had assisted our wins, taking stock of the armaments and protocols that we have developed over the years, identification of chinks in our armour and inventing new tools and reform measures to face present and future challenges.
Thankfully, the number of confirmed cases of COVID-19 and reported deaths from the disease in India are much less compared to the numbers reported from many other countries in the world. Yet, the new infection is an added burden.
Infectious diseases resulting from other microbes are even now major causes of human morbidity and mortality resulting in heavy healthcare expenditure in India. Despite notable successes in the control of major epidemic diseases such as malaria, plague, leprosy and cholera in the past, in recent times, our country has had outbreaks and epidemics of many infectious diseases. Respiratory viral infections, insect borne and bat-borne viral infections are three major types of emerging viral infections in India. New infectious agents have also been noted. The economic impact of infections can be enormous because of high costs of medical care, number of days of productive work lost due to ill-health, impact on travel and tourism and reduced export of agricultural produce and fishery products from affected regions. The psychological impact has not been assessed.
The challenges in the control and prevention of emerging and re-emerging infectious diseases range from understanding the factors contributing for the emergence, to adequately strengthening the surveillance systems. Geo-climatic differences, uneven population, socio-cultural and ecological factors are added challenges. About 60 % of infectious diseases and 70 % per cent of emerging infections of humans are those that spread from animals, with two-thirds originating in wildlife. Random urbanization has placed humans at increasing contact with animal and insect vectors of viral infections.
In a very recent review in the Indian Journal of Medical Research Devendra T Mourya and colleagues from the ICMR-National Institute of Virology, Pune concluded that “There is a need for strengthening disease surveillance in the country focusing on the epidemiology and disease burden. There is also a pressing need to gain detailed insights into disease biomics, including vector biology and environmental factors influencing the diseases. It is also important to strengthen the emergency preparedness for these diseases and response”.
World Health Organization has recommended several strategies to strengthen epidemic preparedness and rapid response, public health infrastructure, risk communication, research and its utilization, and advocacy for political commitment and partnership building. Several initiatives are already underway in our country.
The Integrated Disease Surveillance Project (IDSP) established initially in 101 districts in 2004 has expanded and presently covers all States and districts in the country. Each district presently has a surveillance unit and a rapid response team.
India has also been implementing various provisions of the International Health Regulations (IHR) to enhance national and thereby global public health security. IHR aims to prevent as well as respond to acute public health risks that have the potential to cross borders and may thus constitute a potential threat to other countries.
The current disaster, though has demonstrated our ability to respond to the immediate demands, it has also exposed our frailty in deployment and further rapid development of specific diagnostics and treatment strategies during unanticipated epidemics. Reasons for these need to be determined.
Despite harboring a population exceeding a billion, India has only about fifty infectious disease specialists. The field of infectious disease certainly needs more emphasis in the medical education system. Curriculums are to be designed to suit the changing needs of the country.
The practice of overuse and misuse of antibiotics, a well-known risk factor for the development of multidrug-resistant organisms, is widespread both among primary-care physicians and specialists in India. Antibiotic prescribing certainly needs to be policed.
Another weakness is insufficient financial support for studies in infectious diseases. We have to seriously consider investing more for collection of strategically useful data for exploiting the benefits of advances in the emerging discipline of Data Science, Epidemiology, Vaccinology and research towards identifying novel targets and developing drugs for infectious disease.
Targets for investments in emerging infectious disease prevention
Several useful measures have been recommended for prevention of emerging infectious diseases. The discovery of new potential human pathogens is one such approach. Given the high cost and uncertainty about its effectiveness, this strategy has several critics.
Individuals in close and frequent contact with wild animals and livestock (e.g., farmers and veterinarians) can act as human sentinels of recent spill over events. If the spill over is rapidly identified, adequate control measures can be taken to prevent the spread of pathogen among the population. Surveillance of pathogens in vectors must also be encouraged and expanded.
Screenings of samples from blood donors may help to detect the circulation of emerging pathogens at a population level. This would certainly necessitate adequate laboratories and technical personnel. A word of caution is that microbial screening in the general population though can be very useful, can also sometimes trigger false alarms. Various microorganisms that circulate in humans are not necessarily disease causing.
Prevention of emerging infectious diseases is also dependent on the strengthening of population access to education and health services as well as environmental preservation. Human, animal, and environmental factors are to be considered together in infectious disease prevention and reduction strategies.
Invention of new cost-effective diagnostic technologies and tools of pathogen detection is crucial. Encouragingly, new diagnostic technologies are on the horizon. DNA microarray platforms capable of detecting several pathogen species in a single biological sample, portable sequencers and CRISPR/Cas-based methods are important new tools for pathogen diagnostics. Rapid and precise microbial detection tools are generally expensive and a desire to implement them in countries such as India is presently ambitious. Nonetheless, investment in the development of new diagnostic technologies can levitate surveillance strategies.
Study of genetic material recovered directly from samples in the environment (Metagenomic strategies) are advantageous to identify which groups of pathogens are present in environmental, animal, or clinical samples. They also permit assessment of the abundance of pathogen categories in the sample. DNA sequences collected can be used to delineate evolutionary aspects of the pathogens, to deduce transmission chains, and even predict the probable initiation of an outbreak. Studies of samples from vectors or wildlife can aid discovery of new pathogens with spill over potential.
Should we eradicate infectious agents?
While ruminating over a definitive approach, it would perhaps also be wise to lend ear to other sane thoughts.
In an Opinion Article published nearly a decade ago in Frontiers in Immunology, Clark Donald Russell from the University of Edinburgh argued that eradicating infectious diseases may not always be beneficial.
He wrote: “Bugs don’t equal disease”. In some instances, infection by pathogenic organisms appears to have beneficial effects for the host and these must be explored to fully understand the consequences of eradicating any infection.
There is evidence that persistent infection results in a long-term, potentially lifelong effect on host immune regulation. The ongoing research into the symbiotic interactions between pathogenic bacteria and their hosts is expected to yield very interesting data. There is a school of thought that humans have co-evolved with microbes and it is too simplistic to consider that eradication of microbial disease would be entirely profitable.
For some infections such as that caused by human immunodeficiency virus (HIV), eradication is clearly a desirable goal. There are others that may require careful thought. The perils of blanket microbe killing is evident in the serious sequelae in patients treated bowel infection by Clostridium difficile. Another example is of Helicobacter pylori that resides in the stomach and is associated with 75% of stomach ulcers and stomach cancer. H. pylori colonization in stomach has reduced significantly, thanks to antibiotic treatment and lowered transmission. This has resulted in a welcome decrease in the incidence of peptic ulcer and stomach cancer. Be that as it may, there is evidence for a reciprocal increase in the incidence of acid reflux disease (GERD), and cancer of the oesophagus. Elimination of H. pylori appears to result also in increased secretion of a hormone that stimulates hunger (ghrelin), by the stomach. There is a hypothesis that the rising incidence of obesity in children is related to increased secretion of ghrelin in the absence of H. Pylori in them. All of these examples reveal how complex the microbe – host interaction is.