Are we prepared for the next disease outbreak?
With growing antimicrobial resistance making existing treatments ineffective, predicting and preventing old and new outbreaks has become more critical than ever before.health Updated: Oct 15, 2017 11:00 IST
Plagues, new and old, are threatening human health like never before. And try as the world may, the responses so never early or adequate enough.
The ongoing outbreak of pneumonic plague, which spreads from person to person through coughing and aerosols, had infected 343 persons and killed 42 in Madagascar on last count.
In the past, Madagascar has reported small outbreaks of bubonic plague, which is transmitted from infected rats to humans by fleas, in isolated rural pockets, but the ongoing outbreak is happening in densely populated towns and cities, including the capital, Antananarivo. Both plagues are caused by the Yersinia pestis bacterium, with the deadlier pneumonic plague developing when untreated bubonic plague spreads to the lungs.
Even as Madagascar battles the “Black Death” that wiped out one-third of Europe’s population in the 14th century, the world is looking for new tools to prepare for both emerging and endemic challenges. With one disease-causing pathogen jumping the species barrier roughly once every year and causing an outbreak in every 10 years, and growing antimicrobial resistance making existing treatments ineffective, predicting and preventing old and new outbreaks has become more critical than ever before.
Six of every 10 infectious diseases in humans are spread from animals. Emerging zoonoses - diseases that are naturally transmittable from animals to humans - have caused six major outbreaks since 2000, including Ebola, which sickened 28,652 people and killed 11,325 since it was first reported in 2014 in Liberia, Sierra Leone and Guinea in west Africa. Initially dismissed as a localised outbreak, the infection spread to seven other countries in Africa, Europe and North America before it could be contained.
Other emerging threats are H7N9, which was first reported in China in 2013, MERS in Saudi Arabia in 2012, H1N1 in Mexico, H5N1 in China in 2003, and SARs again in China in 2002. Since 2000, six new outbreaks have created fears of pandemics. The H5N1 outbreak in 2003-06, which has killed infected 859 people and killed 453 --- more than half of those infected -- and the H1N1 pandemic in 2009-10, are chilling reminders of the flu virus’ quicksilver capability for recombination and re-assortment to jump between species through close contact with infected poultry, wild birds and animals, both dead and alive, and contaminated surfaces
Most emerging disease threats come from variants of the bird flu virus subtypes (H5N1, H7N9, H9N2) and swine flu virus subtypes (H1N1, H3N2). Outbreaks occur when viruses recombine - H1N1 is a triple reassertant influenza virus containing human, swine and Eurasian avian flu strains - spread directly between humans, as did H1N1, which caused a pandemic in 2009-10 to infect humans in five continents within months.The next big threat pandemic threat is likely to be from a bird flu virus, which has prompted the US Centers of Disease Control & Prevention to classify avian influenza viruses as “viruses of special concern”.
“One health” solution
Changing interactions between people, animals and the environment is leading to the emergence and re-emergence of many diseases. Increasing mobility, intensified animal production for food, rapid urbanisation, decreasing biodiversity and climate change are creating hotbeds for infection. Rising global temperature, for example, is expanding the potential habitat for mosquitoes and ticks, which can carry infection from endemic areas to new territories.
The interplay between human, animals and ecosystems requires a trans-disciplinary One Health approach to monitor, predict and control potential public health threats. Last week, global experts - including epidemiologist, physicians, veterinarians, ecologists, social scientists and community leaders - met at Uppsala Health Summit on Tackling Infectious Diseases to recommend and adopt collaborative policies and interventions that can be adapted by communities across the world to quickly report and contain outbreaks.
Animals share human susceptibility to some diseases and environmental hazards, and this makes them early warning signs of potential human illness. For example, birds often die of avian influenza and West Nile virus before people get sick, which makes it possible for veterinarians and public health experts to collaborate to prevent outbreaks in humans. Collaboration will also help in mosquito and other vector-control to contain endemic infections such as malaria, dengue, Zika and chikungunya.
Zoonoses not only devastate human health but also affect food safety, food production, animal health, livelihoods, national economies and, if the outbreak is not contained, international travel and trade. Almost all infections are less than 48 hours away, the average time it takes for symptoms to appear after a person gets infected. Because if people are symptom free, there is no way of knowing if they are infected or not.