It was the best of times, it was the worst of times: a tale of two cities-Beijing and Shanghai-why the divergent COVID-19 control outcomes?

Coronavirus disease 2019 (COVID-19) both creates and complicates public health challenges. Yet, the pandemic also provides a unique lens for dissecting complex issues in global health that could benefit society in the long run. In this article, we discuss the underlying reasons that can help explain the divergent COVID-19 control outcomes between Beijing and Shanghai-two advanced metropolises that are similar in their municipal capacity, administrative capability and pandemic strategy. We hope insights from this investigation contribute to the development of disease prevention systems, such as context-specific and data-driven public health strategies that could yield optimal pandemic control outcomes with minimal unintended consequences, both amid and beyond COVID-19.

Short-term induction of alkaloid production in lupines Differences between N2-fixing and nitrogen-limited plants.

We used N2-fixing and nonfixing lupines to examine the effects of plant nutrition on short-term alkaloid production in damaged leaves. Three different treatments were used: damaged leaves from N2-fixing plants; undamaged leaves from these damaged, N2-fixing plants; and damaged leaves on nitrogen-limited, nonfixing plants. Relative to controls, alkaloids increased in concentration more quickly in the N2-fixing than in the nitrogen-limited plants. The magnitude of this increase in alkaloids was correlated with the initial alkaloid concentration. These results suggest that nitrogen-rich plants may benefit from faster and higher alkaloid induction than nitrogen-limited plants. In addition, the detailed dynamics of individual alkaloids are consistent with earlier proposals for the mechanism of lupine alkaloid induction.

Effects of dietary protein and lupine alkaloids on growth and survivorship ofSpodoptera eridania.

Toxic chemicals and nutrients are often positively correlated within and among plants. We studied how such correlations affect the suitability of plants as food for herbivores by assessing the growth and survivorship ofSpodoptera eridania (army worm) on artificial diets containing lupine alkaloids and casein. We found that (1) the effects of casein were determined by other dietary components: increased dietary casein led to increased larval growth only when the diet was also high in wheat germ. (2) Dietary alkaloids were effective at very low concentrations, reducing both growth and survivorship. The alkaloids lupanine and sparteine were not synergistic in their effects, and the interaction between alkaloids and casein was significant only in the low-wheat-germ diets. (3) The effects of casein and alkaloids were generally apparent only in the first instar, and the growth of fifth-instar larvae was unaffected by diet. (4) Using these artificial diet experiments, we can make simple predictions about the food quality of plants grown under various nutrient regimes. These predictions are consistant with recent ideas about optimal plant defenses.

The effects of nitrogen fixation, soil nitrate, and defoliation on the growth, alkaloids, and nitrogen levels of Lupinus succulentus (Fabaceae).

We examined the effects of nitrogen nutrition and defoliation on the alkaloids, nitrogen levels, and growth of Lupinus succulentus by growing plants under five nitrogen/defoliation treatments: 1) fertilization with a high-nitrate nutrient solution, 2) fertilization with a low-nitrate solution, 3) inoculation with N-fixing bacteria but without available soil nitrogen, 4) high-nitrate solution plus periodic partial defoliation, and 5) low-nitrate plus defoliation. In the absence of defoliation, plants from both the N-fixing and high-N treatments had higher concentrations of alkaloids and nitrogen, and higher growth rates than the low-N plants. Periodic defoliation had little effect on the high-N plants, but defoliated N-fixing plants were severely stunted and had lower alkaloid and nitrogen levels. The experimental treatments also affected the relative concentrations of the alkaloids. Our results indicate that 1) alkaloid composition and concentration in L. succulentus are determined by both nitrogen availability and developmental state, 2) plants relying solely on N-fixation respond quite differently to defoliation than those with adequate soil nitrogen, and 3) the food value of the plant tissue can be affected by an interaction between the effects of defoliation and nitrogen status.

Nitrogen fixation by intact colonies of the termite Nasutitermes corniger.

Whole colonies of the arboreal termite Nasutitermes corniger (lsoptera, Termitidae, Nasutitermitinae) from a Costa Rican rainforest were assayed for nitrogen fixation by the acetylene reduction method, using a 21-1 test chamber. Nitrogenase activity was positively correlated with termite biomass for the nexts examined, providing the experiment was performed within 2 h of removal of the colony from the field. Total colony fixation rates of 0.25-1.0 mg N per colony per hour indicate a nitrogen doubling time of 200-600 days, thereby making possible complete replacement of the nest population 1-2 times per year.

Effects of desiccation and rehydration on nitrogen fixation by epiphylls in a tropical rainforest.

Nitrogen fixation rates by epiphyllous microorganisms are affected by desiccation. Rates from leaf samples which had been dried for 12 h were 0.66 ng N/10 cm(2)/h. In contrast, rates from leaves which had been kept continuously wet were 18.69 ng N/10 cm(2)/h. Leaf samples which had been rehydrated for 2 and 4 h showed intermediate fixation rates (4.26 and 9.76 ng N/10 cm(2)/h, respectively). Epiphyllous bryophytes maintain moist conditions on the leaf surface and thus create a microenvironment suitable for prolonged fixation by the microorganisms.

Nitrogen sources for neotropical nasute termites: Fixation and selective foraging.

Studies with Nasutitermes and Rhynchotermes (Isoptera, Nasutitermitinae) in a Costa Rican rainforest suggest that nitrogen fixation by gut symbionts may play a significant role in termite nutrition. Leaf-litter feeders ingest more and fix less nitrogen than do wood-litter feeders; both species feed preferentially on N-rich foods in their foraging repertoire. Unusually high N2 fixation (acetylene reduction) rates were found in Nasutitermes soldiers, thereby reducing their nutritional dependence on workers. Finally, N2 fixation rates of termites diminished rapidly within 24 h after removal of a colony from the field, underlining the importance of conducting future N2 fixation studies under field conditions.