Like an intermittent fever which spikes at intervals, media coverage of infectious diseases rises to high pitch whenever a new killer outbreak is reported anywhere in the world. The fear of global spread alarms the general public and keeps public health agencies on high alert. This has been true in recent years, with SARS, H5N1, H1N1, MERS, Ebola, Zika, and Nipah viruses becoming familiar names in the rogues’ gallery of viruses that move from animals to humans. The interval between these spikes has been shortening over the past five decades, even as media’s speed in spreading scary news has increased markedly. So, it feels as though we are under siege most of the time, with viral marauders reported regularly across our highly connected world.
In the past fortnight, spotlight has been on Nipah in India and the return of Ebola in Africa. Both are viruses with high mortality rates and the fear of acquiring infection from patients is terrifying communities around them, and causing concern in even those who are far away. We have seen the anti- social, stigmatising behaviour of bus commuters in Kerala refusing entry to nurses who are not ill, even as the state and the country salute the selfless sacrifice of Nurse Lini.
A rational response to such outbreaks requires an understanding of why these viruses cross species, how they are transmitted among humans, what preventive measures can be taken, which tests and treatments exist, and whether the health system is ready to contain the outbreak at an early stage.
Joshua Lederberg, who was awarded the Nobel Prize for his discoveries in bacterial genetics, says that an axiomatic starting point for further progress is the simple recognition that humans, animals, plants, and microbes are co-habitants of the planet. Instabilities arise in this dynamic relationship because of ecological and evolutionary causes.
Zoonotic diseases (transmitted from animals to humans), account for over 60% of infectious outbreaks. Deforestation due to expanding agriculture and logging, animal breeding, and live stock farming are creating a conveyor belt for the transmission of microbes, hitherto confined to their primary animal hosts in wild life, to the veterinary population and then to human habitats. Anthropogenic climate change creates conditions for vectors like mosquitoes and ticks to spread to new geographies. They transport the microbes to the human body. Man thus falls victim to his own ecological follies. Bats did not choose to live amongst us—we forced them to become part of our expanding habitat.
Evolutionary forces then take over. Microbial genetics evolve far more rapidly than humans. Microbes which are confined to forest animals or small human communities follow the survival rules of evolution, and generally have low virulence, because the extinction of their host will lead to their own extinction.
However, humans now crowd together in large numbers, travel fast and far in many modes of transport, and unknowingly transmit microbes to other humans through sputum, saliva, semen, blood, and other bodily fluids. This enables the virus to multiply rapidly and mutate to more virulent forms.
Now, even if it kills over half of those it infects, there is still a large host population remaining to ensure its own survival and propagation. Generally, highly transmissible strains (like H1N1), are not highly virulent and highly virulent strains (like H5N1), are not highly transmissible.
So, the seesaw of survival maintains a balance between microbes and humans. However, microbes must be vigilantly monitored during outbreaks to study if highly infective viruses are suddenly seized with mutation madness to develop higher virulence, especially in crowded populations where the virus has a free run.
David Quammen succinctly states in Spillover, a brilliant biography of zoonoses, “Ecological circumstance provides the opportunity for spillover. Evolution seizes the opportunity, explores possibilities, and helps convert spillovers to pandemics”.
Vaccines are presently not available against many of these viruses, though some early success has been reported in candidate vaccines for Ebola and Zika. Specific drug treatments too, are unavailable. Laboratory diagnosis is possible in specialised labs but is mainly useful for identifying the nature of the outbreak, modelling its likely spread, and alerting the health system of the anticipated clinical severity of the cases that will arise.
India is now expanding its laboratory network but epidemiological surveillance systems need further strengthening. In the absence of specific treatments, supportive care has to be provided: fluids for adequate hydration and electrolyte balance; medicines to control fever, and intensive care with respiratory and circulatory support when needed.
During any outbreak, isolation of the patient, avoidance of direct contact while providing care, tracing, examination of all contacts, and limiting their movement during the incubation period will help to contain the spread. Preventive measures include hand washing and avoiding contact with bodily fluids of a person known or suspected to be infected. Avoidance of direct or indirect contact with animals, who act as primary or reservoir hosts, is necessary.
Effective risk communication to the public is especially necessary, to enable them to adopt preventive personal protection measures, seek timely medical care, and avoid mass panic. This requires clear and open information sharing by trusted experts who are adept in jargon-free messaging via mass media. Reporting by the media should exercise responsible restraint to avoid stoking mass hysteria.
Lederberg says we should stop talking of a ‘war on microbes’ to eradicate them, and replace the war metaphor with an ecological metaphor, so that humans and microbes can co-exist without mutual destruction. This is especially true of zoonotic viruses which have animals as primary hosts.
However, the health system must be well prepared to handle outbreaks of pathogenic microbes with good surveillance systems, effective containment measures, development of new vaccines and treatments, and severity-based clinical care protocols. In the words of that Nobel Laureate, who first unraveled microbial genetics, “it is our wits against their genes.” Our wits should teach us how to respect planetary health even as we zealously protect human health.
Writer is President, Public Health Foundation of India
Views expressed are personal