Why does COVID-19 case fatality rate vary among countries?

BackgroundWhile the epidemic of SARS-CoV-2 is spreading worldwide, there is much concern over the mortality rate that the infection induces. Available data suggest that COVID-19 case fatality rate varies temporally (as the epidemic progresses) and spatially (among countries). Here, we attempted to identify key factors possibly explaining the variability in case fatality rate across countries. MethodsWe used data on the temporal trajectory of case fatality rate provided by the European Center for Disease Prevention and Control, and country-specific data on different metrics describing the incidence of known comorbidity factors associated with an increased risk of COVID-19 mortality at the individual level (Institute for Health Metrics and Evaluation). We also compiled data on demography, economy and political regimes for each country. FindingsWe first showed that temporal trajectories of case fatality rate greatly vary among countries. We found no evidence for association between comorbidities and case fatality rate at the country level. Case fatality rate was negatively associated with number of hospital beds x1,000 inhabitants. We also report evidence suggesting an association between case fatality rate and the political regime, with democracies suffering from the highest mortality burden, compared to autocratic regimes. However, most of the among-country variance in case fatality rate remained unexplained. InterpretationOverall, these results emphasize the role of socio-economic and political factors as possible drivers of COVID-19 case fatality rate at the country level. FundingNone.

Intestinal Parasitic Infections and Environmental Water Contamination in a Rural Village of Northern Lao PDR

A field survey studying intestinal parasites in humans and microbial pathogen contamination at environment was performed in a Laotian rural village to identify potential risks for disease outbreaks. A parasitological investigation was conducted in Ban Lak Sip village, Luang Prabang, Lao PDR involving fecal samples from 305 inhabitants as well as water samples taken from 3 sites of the local stream. Water analysis indicated the presence of several enteric pathogens, i.e., Aeromonas spp., Vibrio spp., E. coli H7, E. coli O157: H7, verocytotoxin-producing E. coli (VTEC), Shigella spp., and enteric adenovirus. The level of microbial pathogens contamination was associated with human activity, with greater levels of contamination found at the downstream site compared to the site at the village and upstream, respectively. Regarding intestinal parasites, the prevalence of helminth and protozoan infections were 68.9% and 27.2%, respectively. Eight helminth taxa were identified in fecal samples, i.e., 2 tapeworm species (Taenia sp. and Hymenolepis diminuta), 1 trematode (Opisthorchis sp.), and 5 nematodes (Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercoralis, trichostrongylids, and hookworms). Six species of intestinal protists were identified, i.e., Blastocystis hominis, Cyclospora spp., Endolimax nana, Entamoeba histolytica/E. dispar, Entamoeba coli, and Giardia lamblia. Questionnaires and interviews were also conducted to determine risk factors of infection. These analyses together with a prevailing infection level suggested that most of villagers were exposed to parasites in a similar degree due to limited socio-economic differences and sharing of similar practices. Limited access to effective public health facilities is also a significant contributing factor.

Bartonella species in small mammals and their potential vectors in Asia

In this article, authors review the current knowledge of Bartonella infection in small mammals including rodents, insectivores, bats and exotic small mammal pets and their vectors in Asia. Species of Bartonella are Gram-negative intracellular bacteria that infect erythrocytes of various mammalian and non-mammalian animals and mainly transmitted by blood sucking arthropod vectors. The genus Bartonella includes several species of important human diseases with severe clinical signs. Several new Bartonella species were isolated from rodents and other small mammals, and from human patients in Asia. Bartonella species are identified using standard polymerase chain reaction amplification and a sequencing targeting two housekeeping genes (gltA and rpoB) and the internal transcribed spacer fragment. Authors also discuss the implications in term of potential emerging zoonotic diseases.

Bartonella species in small mammals and their potential vectors in Asia

In this article, authors review the current knowledge of Bartonella infection in small mammals including rodents, insectivores, bats and exotic small mammal pets and their vectors in Asia. Species of Bartonella are Gram-negative intracellular bacteria that infect erythrocytes of various mammalian and non-mammalian animals and mainly transmitted by blood sucking arthropod vectors. The genus Bartonella includes several species of important human diseases with severe clinical signs. Several new Bartonella species were isolated from rodents and other small mammals, and from human patients in Asia. Bartonella species are identified using standard polymerase chain reaction amplification and a sequencing targeting two housekeeping genes (gltA and rpoB) and the internal transcribed spacer fragment. Authors also discuss the implications in term of potential emerging zoonotic diseases.

Specific primers for PCR amplification of the ITS1 (ribosomal DNA) of Trypanosoma lewisi.

Trypanosoma lewisi is a mild or non-pathogenic parasite of the sub-genus Herpetosoma transmitted by fleas to rats. In a previous study we described pan-trypanosome specific primers TRYP1 which amplify the ITS1 of ribosomal DNA by hybridizing in highly conserved regions of 18S and 5.8S genes. These primers proved to be useful for detecting T. lewisi DNA in laboratory rats, but a recent large scale survey in wild rodents demonstrated a lack of specificity. In the present study, we designed and evaluated mono-specific primers LEW1S and LEW1R, for the detection and identification of T. lewisi by a single-step PCR. These primers were designed inside the highly variable region of the ITS1 sequence of T. lewisi ribosomal DNA. The product size of 220 bp is specific to T. lewisi. The sensitivity limit was estimated between 0.055 and 0.55 pg of DNA per reaction, equivalent to 1-10 organisms per reaction. All the PCR products obtained from 6 different T. lewisi isolates were more than 98% similar with each other and similar to the sequences of T. lewisi already published in Genbank. All DNA of 7 T. lewisi stocks from China gave the specific 220 bp product. We showed that LEW1S and LEW1R primers enabled sensitive detection and identification of T. lewisi infection in laboratory and wild rats. This assay is recommended for monitoring T. lewisi infections in rat colonies or for studying infections in the wild fauna. An absence of cross reaction with human DNA means that these primers can be used to investigate atypical trypanosome infections in humans. Given the risk of T. lewisi infection in human, we believe that these primers will be beneficial for public health diagnosis and rodents investigation programmes.