Health Threats

Interview: Infectious diseases are resurfacing in forms that are difficult to treat

Dr Richard Cash, who helped develop oral rehydration therapy for cholera, on India’s vulnerability to drug-resistant infections.

Since 2016, the Sindh province of Pakistan has been in the grip of a typhoid outbreak. Researchers from Britain’s Wellcome Sanger Institute who analysed the typhoid strain have linked the outbreak to an extensively drug-resistant superbug.

Dr Richard Cash, senior lecturer on global health from the Harvard TH Chan School of Public Health, believes such outbreaks will become more common as drug resistance leads to the re-emergence of infectious diseases around the world.

Speaking to medical students at Seth GS Medical College in Mumbai in February, Cash stressed on the need to prevent these infections, instead of relying on treatment with antibiotics to counter this threat. He said that the spread of drug-resistant infections coupled with a shortage of medicines could lead to higher drug prices, leaving fewer people able to afford them.

Cash has spent five decades working with health systems in South Asia and is among the group of doctors who conducted the first clinical trial on oral rehydration therapy, which has proved to be the most cost-effective intervention to treat patients infected with cholera and other diarrhoeal diseases. He spoke to on the new global threats from infectious diseases. Here are edited excerpts from the interview.

How far-reaching is the threat from drug-resistant infections and why are we unable to produce more effective antibiotics to control them?
There are a number of examples of where organisms have developed resistance to specific antibiotics or where the dose of antibiotics needed for treatment have increased. Cholera is now resistant to tetracycline in many areas of the world including Bangladesh. Fortunately, there are other antibiotics that can still be used. Resistance to gonorrhea has dramatically increased globally and in some regions it is virtually untreatable with antibiotics. Other infections will certainly follow this pattern. Scientifically, it is difficult to develop a new class of antibiotics, that is, acting through a different mechanism. Also, there is not a strong economic incentive for pharmaceutical companies to engage in product development as new antibiotics will have to be priced so that they are affordable and treatment is usually short-term.

What infections do you fear might re-emerge? India is already grappling with the problem of drug-resistant tuberculosis.
New and re-emergent diseases are as much of a problem in India as anywhere. Multiple drug-resistant tuberculosis is already a problem and will likely increase as the necessary drugs must be distributed to wherever the diagnosis is made. Artemisinin-resistant malaria has already begun to make inroads and its incidence will also increase.

As to new diseases, the population density and movement into new areas will enhance spread as will the poor hospital infection control that exists in many institutions. The early detection of these diseases will depend on the quality of disease surveillance, which is lacking in many geographic areas. The vector for yellow fever is here in India but the disease has not, as yet, been introduced. We still don’t know why.

Why do you think countries like India have failed to control the spread of infections? You spoke about the problem of open defecation in India and its role in fuelling infections. Could you elaborate?
Building toilets does not ensure their use. From a health perspective the impact of reducing open defecation would be to decrease the presence of faeces related pathogens in the environment, including reducing contamination of surface water. Additionally, it has been postulated that open defecation contributes to tropical enteropathy which is seen as a risk factor for nutritional stunting.

I have not recently traveled to urban or rural India where the Swachh Bharat Mission is very active so I cannot comment on the quality of the construction, the use of toilets and why (water shortages, lack of connections, culture etc), their impact, and the quality of the evaluation. But a number of articles have questioned the validity of government statistics on all of these issues. The issue of caste has been raised by some as a barrier to cleaning and maintenance of toilets and though manual scavenging is supposedly outlawed or controlled, in many areas it clearly persists.

Dengue and chikungunya ward at Aruna Asaf Ali Hospital in New Delhi. (Saumya Khandelwal/HT File Photo)
Dengue and chikungunya ward at Aruna Asaf Ali Hospital in New Delhi. (Saumya Khandelwal/HT File Photo)

We have also relied on vaccines to prevent infectious diseases. But, there is a growing resistance against vaccine globally as well as in India.
Regarding vaccines, public health is, in many ways, a victim its own success. We do not have a number of diseases because of the widespread use of vaccines (smallpox, polio, tetanus etc) and the incidence of others has been greatly reduced (measles etc). This has led some to question why we need vaccines for these conditions since we do not have the disease. But unless a disease has been eradicated (that is, globally eliminated) we need to keep immunising. Natural immunity is attainable for some diseases (but not tetanus, for example) but at a cost – disease with associated morbidity and mortality or persistent carriage of bacteria or virus.

For a new vaccine to be introduced (rotavirus, pneumococcal, Hib etc), vigorous evaluation of effectiveness, safety, and cost must be done as a vaccine is a product given to an otherwise healthy person. Whether a vaccine is made available or introduced into a national program will depend on its effectiveness, safety, acceptability, cost etc. These determinations are made by expert committees here in India which would seem to have little to gain financially (unless there’s a clear conflict of interest). Chronic hepatitis B infection is a major risk factor for the development of cirrhosis and hepatocellular carcinoma yet hepatitis B infection is easily prevented by a very effective and inexpensive vaccine. Wide use of vaccines produce health equity and in some cases their use could reduce the need for overused antibiotics.

Your work with the discovery of oral rehydration therapy for cholera shows that simple solutions can help treat deadly conditions. Do you think that medical community is focusing more on expensive treatments and has forgotten to look for easy solutions and preventive strategies to control diseases?
There has always been a tension between the very best intervention (however and whoever defines defines this) versus one that may not be perfect but reaches a far larger population at a reduced cost. That was the case in the development of Oral Rehydration Therapy. Drug companies are business trying to maximise profits and that should not be forgotten. But often low-cost, widely used products command a much higher profit than high-cost infrequently used products.

There is a growing trend among developing economies to revise its health strategies and accommodate interventions to control non-communicable diseases. Is this a misplaced priority given that many countries including India have a large proportion of disease burden as a result of infectious diseases?
The problem of non-communicable diseases is actually of greater importance in lower income countries in terms of the numbers (over 80% of the global burden, the earlier age of onset , later diagnosis, and often incomplete or not well managed treatment. India still has a double burden of both infectious diseases and non-communicable diseases, some of which are triggered by infections. But that is no reason to ignore the impact, prevention, or treatment of non-communicable diseases.

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