Infectious diseases: Predictions of virus spillover across species

Backyard zoonoses: The roles of companion animals and peri-domestic wildlife

The spillover of human infectious diseases from animal reservoirs is now well appreciated. However, societal and climate-related changes are affecting the dynamics of such interfaces. In addition to the disruption of traditional wildlife habitats, in part because of climate change and human demographics and behavior, there is an increasing zoonotic disease risk from companion animals. This includes such factors as the awareness of animals kept as domestic pets and increasing populations of free-ranging animals in peri-domestic environments. This review presents background and commentary focusing on companion and peri-domestic animals as disease risk for humans, taking into account the human-animal interface and population dynamics between the animals themselves.

Highly coordinated nationwide massive travel restrictions are central to effective mitigation and control of COVID-19 outbreaks in China

COVID-19, the disease caused by the novel coronavirus 2019, has caused grave woes across the globe since it was first reported in the epicentre of Wuhan, Hubei, China, in December 2019. The spread of COVID-19 in China has been successfully curtailed by massive travel restrictions that rendered more than 900 million people housebound for more than two months since the lockdown of Wuhan, and elsewhere, on 23 January 2020. Here, we assess the impact of China's massive lockdowns and travel restrictions reflected by the changes in mobility patterns across and within provinces, before and during the lockdown period. We calibrate movement flow between provinces with an epidemiological compartment model to quantify the effectiveness of lockdowns and reductions in disease transmission. Our analysis demonstrates that the onset and phase of local community transmission in other provinces depends on the cumulative population outflow received from the epicentre Hubei. Moreover, we show that synchronous lockdowns and consequent reduced mobility lag a certain time to elicit an actual impact on suppressing the spread. Such highly coordinated nationwide lockdowns, applied via a top-down approach along with high levels of compliance from the bottom up, are central to mitigating and controlling early-stage outbreaks and averting a massive health crisis.

Emergence of synergistic and competitive pathogens in a coevolutionary spreading model

Cooperation and competition between pathogens can alter the amount of individuals affected by a coinfection. Nonetheless, the evolution of the pathogens' behavior has been overlooked. Here, we consider a coevolutionary model where the simultaneous spreading is described by a two-pathogen susceptible-infected-recovered model in an either synergistic or competitive manner. At the end of each epidemic season, the pathogens species reproduce according to their fitness that, in turn, depends on the payoff accumulated during the spreading season in a hawk-and-dove game. This coevolutionary model displays a rich set of features. Specifically, the evolution of the pathogens' strategy induces abrupt transitions in the epidemic prevalence. Furthermore, we observe that the long-term dynamics results in a single, surviving pathogen species, and that the cooperative behavior of pathogens can emerge even under unfavorable conditions.

Fault Lines in India's COVID-19 Management: Lessons Learned and Future Recommendations

With about 0.4–0.5 million COVID cases diagnosed every single day in a row over the past three weeks back in May 2021, India was at the epicenter of the global viral rampage. The catastrophe of this crisis was unprecedented, pushing the health care system to its breaking point. Although significant progress has been made in identifying these highly transmissible variants, what is somewhat lacking is the competence to exploit this information for risk mitigation and effective disease management through an integrated nationwide coordinated approach. With a positivity rate of 15–20% (April–May 2021) and the healthcare system pushed to its limit, accompanied by increased mortality, the situation was rather grim then. Though the central command scrambled all its resources and logistics to streamline the supply chain, the efforts were insufficient in response to the ongoing crisis due to a disproportionate rise in the case. We examined the current scenario emerging from this 2nd COVID wave and identified the possible lacunae. We also suggested few recommendations that may be adopted to avoid similar failures in the future.

Oscillatory dynamics in the dilemma of social distancing

Social distancing as one of the main non-pharmaceutical interventions can help slow down the spread of diseases, like in the COVID-19 pandemic. Effective social distancing, unless enforced as drastic lockdowns and mandatory cordon sanitaire, requires consistent strict collective adherence. However, it remains unknown what the determinants for the resultant compliance of social distancing and their impact on disease mitigation are. Here, we incorporate into the epidemiological process with an evolutionary game theory model that governs the evolution of social distancing behaviour. In our model, we assume an individual acts in their best interest and their decisions are driven by adaptive social learning of the real-time risk of infection in comparison with the cost of social distancing. We find interesting oscillatory dynamics of social distancing accompanied with waves of infection. Moreover, the oscillatory dynamics are dampened with a non-trivial dependence on model parameters governing decision-makings and gradually cease when the cumulative infections exceed the herd immunity. Compared to the scenario without social distancing, we quantify the degree to which social distancing mitigates the epidemic and its dependence on individuals’ responsiveness and rationality in their behaviour changes. Our work offers new insights into leveraging human behaviour in support of pandemic response.

Soil pathogens that may potentially cause pandemics, including severe acute respiratory syndrome (SARS) coronaviruses

Soil ecosystems contain and support the greatest amount of biodiversity on the planet. A majority of this diversity is made up of microorganisms, most of which are beneficial for humans. However, some of these organisms are considered human pathogens. In light of the current severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) outbreak, one may ponder the origin of the next pandemic and if soil may represent a source of pathogens with pandemic potential. This review focuses on several bacterial, fungal, and viral pathogens that can result in human infection due to direct interaction with the soil. Moreover, the current status of knowledge regarding SARS-CoV-2 survival in and transmission from soil is reviewed.

Global estimates of mammalian viral diversity accounting for host sharing

Present estimates suggest there are over 1 million virus species found in mammals alone, with about half a million posing a possible threat to human health. Although previous estimates assume linear scaling between host and virus diversity, we show that ecological network theory predicts a non-linear relationship, produced by patterns of host sharing among virus species. To account for host sharing, we fit a power law scaling relationship for host-virus species interaction networks. We estimate that there are about 40,000 virus species in mammals (including ~10,000 viruses with zoonotic potential), a reduction of two orders of magnitude from present projections of viral diversity. We expect that the increasing availability of host-virus association data will improve the precision of these estimates and their use in the sampling and surveillance of pathogens with pandemic potential. We suggest host sharing should be more widely included in macroecological approaches to estimating biodiversity.

Emerging infectious disease prevention: Where should we invest our resources and efforts?

Strategies focused on the prevention of emerging infectious disease outbreaks are currently in the spotlight of discussions among researchers committed to infectious disease control. In this mini-review, we provided a brief update on this discussion and characterized the three main targets for investments in emerging infectious disease prevention: animals, human sentinels for spillover events, and the general human population. Furthermore, the pros and cons of each target are highlighted. Despite the particularities of the proposed targets, each of them can fill different gaps in the surveillance of infectious diseases. When all three targets are focused on together, they create a powerful strategy of emerging infectious disease prevention.