The impact of global warming on insect-borne diseases and on highland malaria in particular remains controversial. Temperature is known to influence transmission intensity through its effects on the population growth of the mosquito vector and on pathogen development within the vector. Spatiotemporal data at a regional scale in highlands of Colombia and Ethiopia supplied an opportunity to examine how the spatial distribution of the disease changes with the interannual variability of temperature. We provide evidence for an increase in the altitude of malaria distribution in warmer years, which implies that climate change will, without mitigation, result in an increase of the malaria burden in the densely populated highlands of Africa and South America.

The war in Tigray region of Ethiopia that started in November 2020 and is still ongoing has brought enormous damage to the health system. This analysis provides an assessment of the health system before and during the war. Evidence of damage was compiled from November 2020 to June 2021 from various reports by the interim government of Tigray, and also by international non-governmental organisations. Comparison was made with data from the prewar calendar year. Six months into the war, only 30% of hospitals, 17% of health centres, 11.5% of ambulances and none of the 712 health posts were functional. As of June 2021, the population in need of emergency food assistance in Tigray increased from less than one million to over 5.2 million. While the prewar performance of antenatal care, supervised delivery, postnatal care and children vaccination was 64%, 73%, 63% and 73%, respectively, but none of the services were likely to be delivered in the first 90 days of the war. A conservative estimate places the number of girls and women raped in the first 5 months of the war to be 10 000. These data indicate a widespread destruction of livelihoods and a collapse of the healthcare system. The use of hunger and rape as a weapon of war and the targeting of healthcare facilities are key components of the war. To avert worsening conditions, an immediate intervention is needed to deliver food and supplies and rehabilitate the healthcare delivery system and infrastructure.

Zika virus is a mosquito-borne pathogen that is rapidly spreading across the Americas. Due to associations between Zika virus infection and a range of fetal maladies 1,2 , the epidemic trajectory of this viral infection poses a significant concern for the nearly 15 million children born in the Americas each year. Ascertaining the portion of this population that is truly at risk is an important priority. One recent estimate 3 suggested that 5.42 million childbearing women live in areas of the Americas that are suitable for Zika occurrence. To improve on that estimate, which did not take into account the protective effects of herd immunity, we developed a new approach that combines classic results from epidemiological theory with seroprevalence data and highly spatially resolved data about drivers of transmission to make location-specific projections of epidemic attack rates. Our results suggest that 1.65 (1.45-2.06) million childbearing women and 93.4 (81.6-117.1) million people in total could become infected before the first wave of the epidemic concludes. Based on current estimates of rates of adverse fetal outcomes among infected women 2,4,5 , these results suggest that tens of thousands of pregnancies could be negatively impacted by the first wave of the epidemic. These projections constitute a revised upper limit of populations at risk in the current Zika epidemic, and our approach offers a new way to make rapid assessments of the threat posed by emerging infectious diseases more generally.On 1 February 2016, the World Health Organization (WHO) designated the ongoing Zika virus epidemic in the Americas as a Public Health Emergency of International Concern (PHEIC), defined as an 'extraordinary event' that 'potentially require[s] a coordinated international response' 6 . This declaration acknowledges the high potential for Zika to establish across the Americas given that its dominant vector, the Aedes aegypti mosquito, is endophilic and occupies an exceptionally broad geographical range 7 . Concern underlying this rare WHO declaration also stems from an association between Zika virus infection in pregnant women and a range of adverse fetal outcomes 2 , most notably congenital microcephaly 1 . As of 30 June 2016, there were 1,674 confirmed cases of microcephaly associated with Zika virus infection in five countries 8 , and there is widespread concern that these numbers could increase further as the virus continues to spread across the Americas 9 .A number of uncertainties surround the future of the Zika epidemic in the Americas, particularly questions about how many women may be at risk of having children with congenital microcephaly and other adverse outcomes associated with Zika virus infection 10 . Of women who become infected with Zika virus during a vulnerable stage of their pregnancy, evidence is emerging that 1-13% may go on to develop congenital microcephaly 2,4,5 .However, the number of women who become infected with Zika virus during that timeframe is difficult to ascertain. One recent study 3 estimat...

Epidemic growth rate, r, provides a more complete description of the potential for epidemics than the more commonly studied basic reproduction number, R0, yet the former has never been described as a function of temperature for dengue virus or other pathogens with temperature-sensitive transmission. The need to understand the drivers of epidemics of these pathogens is acute, with arthropod-borne virus epidemics becoming increasingly problematic. We addressed this need by developing temperature-dependent descriptions of the two components of r—R0 and the generation interval—to obtain a temperature-dependent description of r. Our results show that the generation interval is highly sensitive to temperature, decreasing twofold between 25 and 35°C and suggesting that dengue virus epidemics may accelerate as temperatures increase, not only because of more infections per generation but also because of faster generations. Under the empirical temperature relationships that we considered, we found that r peaked at a temperature threshold that was robust to uncertainty in model parameters that do not depend on temperature. Although the precise value of this temperature threshold could be refined following future studies of empirical temperature relationships, the framework we present for identifying such temperature thresholds offers a new way to classify regions in which dengue virus epidemic intensity could either increase or decrease under future climate change.

Zika virus is a mosquito-borne pathogen that is rapidly spreading across the Americas 1 . Due to a probable association between Zika virus infection and a congenital neurological disorder called microcephaly 2 , the epidemic trajectory of this viral infection poses a significant concern for the nearly 15 million children born in the Americas each year. The potential magnitude of the ongoing Zika epidemic is exceedingly difficult to gauge based on existing data 3 , due to a number of uncertainties that cloud the relationship between observed cases and true infections. As an alternative to methods that depend on unreliable case data, we developed and applied a new method that leverages highly spatially resolved data about drivers of Zika transmission to project that 1.1 (1.0-1.9) million infections in childbearing women and 64.2 (53.6-108.1) million infections across all demographic strata could occur before the first wave of the epidemic concludes. Our projection is largely consistent with annual, region-wide estimates of 53.8 (40.0-71.8) million infections by dengue virus 4 , which has many similarities to Zika. Our projection is also consistent with state-level data from Brazil on confirmed, Zika-associated microcephaly cases 5 , and it suggests that the current epidemic has the potential to negatively impact tens of thousands of pregnancies. These projections constitute an important early contribution to efforts to understand the potential magnitude of the Zika epidemic, and our methods offer a new way to make rapid assessments of the threat posed by emerging infectious diseases.

Despite a long history of mosquito-borne virus epidemics in the Americas, the impact of the Zika virus (ZIKV) epidemic of 2015–2016 was unexpected. The need for scientifically informed decision-making is driving research to understand the emergence and spread of ZIKV. To support that research, we assembled a data set of key covariates for modeling ZIKV transmission dynamics in Colombia, where ZIKV transmission was widespread and the government made incidence data publically available. On a weekly basis between January 1, 2014 and October 1, 2016 at three administrative levels, we collated spatiotemporal Zika incidence data, nine environmental variables, and demographic data into a single downloadable database. These new datasets and those we identified, processed, and assembled at comparable spatial and temporal resolutions will save future researchers considerable time and effort in performing these data processing steps, enabling them to focus instead on extracting epidemiological insights from this important data set. Similar approaches could prove useful for filling data gaps to enable epidemiological analyses of future disease emergence events.

Vector-borne diseases display wide inter-annual variation in seasonal epidemic size due to their complex dependence on temporally variable environmental conditions and other factors. In 2014, Guangzhou, China experienced its worst dengue epidemic on record, with incidence exceeding the historical average by two orders of magnitude. To disentangle contributions from multiple factors to inter-annual variation in epidemic size, we fitted a semi-mechanistic model to time series data from 2005–2015 and performed a series of factorial simulation experiments in which seasonal epidemics were simulated under all combinations of year-specific patterns of four time-varying factors: imported cases, mosquito density, temperature, and residual variation in local conditions not explicitly represented in the model. Our results indicate that while epidemics in most years were limited by unfavorable conditions with respect to one or more factors, the epidemic in 2014 was made possible by the combination of favorable conditions for all factors considered in our analysis.

A counterargument to the importance of climate change for malaria transmission has been that regions where an effect of warmer temperatures is expected, have experienced a marked decrease in seasonal epidemic size since the turn of the new century. This decline has been observed in the densely populated highlands of East Africa at the center of the earlier debate on causes of the pronounced increase in epidemic size from the 1970s to the 1990s. The turnaround of the incidence trend around 2000 is documented here with an extensive temporal record for malaria cases for both Plasmodium falciparum and Plasmodium vivax in an Ethiopian highland. With statistical analyses and a process-based transmission model, we show that this decline was driven by the transient slowdown in global warming and associated changes in climate variability, especially ENSO. Decadal changes in temperature and concurrent climate variability facilitated rather than opposed the effect of interventions.