Intra-species sialic acid polymorphism in humans: a common niche for influenza and coronavirus pandemics?

Have Diagnostics, Therapies, and Vaccines Made the Difference in the Pandemic Evolution of COVID-19 in Comparison with "Spanish Flu"?

In 1918 many countries, but not Spain, were fighting World War I. Spanish press could report about the diffusion and severity of a new infection without censorship for the first-time, so that this pandemic is commonly defined as "Spanish flu", even though Spain was not its place of origin. "Spanish flu" was one of the deadliest pandemics in history and has been frequently compared with the coronavirus disease (COVID)-19 pandemic. These pandemics share similarities, being both caused by highly variable and transmissible respiratory RNA viruses, and diversity, represented by diagnostics, therapies, and especially vaccines, which were made rapidly available for COVID-19, but not for "Spanish flu". Most comparison studies have been carried out in the first period of COVID-19, when these resources were either not yet available or their use had not long started. Conversely, we wanted to analyze the role that the advanced diagnostics, anti-viral agents, including monoclonal antibodies, and innovative COVID-19 vaccines, may have had in the pandemic containment. Early diagnosis, therapies, and anti-COVID-19 vaccines have markedly reduced the pandemic severity and mortality, thus preventing the collapse of the public health services. However, their influence on the reduction of infections and re-infections, thus on the transition from pandemic to endemic condition, appears to be of minor relevance. The high viral variability of influenza and coronavirus may probably be contained by the development of universal vaccines, which are not easy to be obtained. The only effective weapon still remains the disease prevention, to be achieved with the reduction of promiscuity between the animal reservoirs of these zoonotic diseases and humans.

Determining half-life of SARS-CoV-2 antigen in respiratory secretion

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is primarily transmitted from person to person through respiratory droplets and aerosols. It is also possible for the virus to be transmitted indirectly through environmental contamination. The likelihood of environmental transmission depends on several factors, including the survival time of the virus in respiratory secretions. However, the stability of SARS-CoV-2 in respiratory secretions has not been investigated. In this study, we compared the half-life of the SARS-CoV-2 antigen in respiratory secretion under different conditions. We applied respiratory secretion (5 µL) to glass slides, air-dried the slides for 1 h, and kept them at 24 °C or 4 °C for 10 days. Respiratory secretions were also placed in test tubes (sealed to preserve moisture) and in normal saline for 10 days. The concentration of SARS-CoV-2 antigen in all samples was simultaneously measured using colloidal gold immunochromatography, and the half-life of the antigen was calculated. The half-life of the antigen in the wet (sealed tube) and saline samples at room temperature was 5.0 and 2.92 days, respectively. The half-life of the antigen in the air-dried sample at room temperature and at 4 °C was 2.93 and 11.4 days, respectively. The half-life was longer in respiratory secretions than that in normal saline. The half-life was also longer in respiratory secretions, at a lower temperature, and under wet conditions. Therefore, environmental transmission can also play a significant role in the spread of the virus. Robust prevention and control strategies could be developed based on the half-life of the antigen in respiratory secretions.

Epidemiologic characteristics of SARS-CoV-2 in Wuhan, other regions of China, and globally based on data gathered from January 2020 to February 2021

This observation study examines coronavirus disease 2019 (COVID-19) data from outbreak and other sites in China and worldwide in order to examine the epidemiological pattern of COVID-19 before the acquisition of immunity through widespread vaccination and infection. COVID-19-related morbidity and mortality data for January 2020 to February 2021 were obtained from the Chinese Center for Disease Control and Prevention, Hubei Provincial Center for Disease Control and Prevention, and the World Health Organization. The number of cases was logarithmically transformed for comparison of the rate of increase or decrease with time across areas. From January to February 2020, the number of new confirmed cases in Wuhan grew substantially but returned to zero by May 2020. In other parts of China, the rate of decrease was lower than that in Wuhan, and the mortality rate was lower outside Wuhan (1.93%) than in Wuhan (7.68%). The influenza trends were similar to those of COVID-19, but the mortality rate of influenza was much lower (0.011%) than that of COVID-19. After the early stage, similar increase in the incidence rate with time was observed globally, although the total number of cases differed between regions. The outbreak severe acute respiratory syndrome coronavirus 2 strain in Wuhan had low epidemic intensity and high virulence, but the epidemiological characteristics of severe acute respiratory syndrome coronavirus 2 may not be associated with race, geography, or economic status. Importantly, more effective prevention and control measures and vaccines should be applied for controlling the variants.

PEDV: Insights and Advances into Types, Function, Structure, and Receptor Recognition

Porcine epidemic diarrhea virus (PEDV) has been endemic in most parts of the world since its emergence in the 1970s. It infects the small intestine and intestinal villous cells, spreads rapidly, and causes infectious intestinal disease characterized by vomiting, diarrhea, and dehydration, leading to high mortality in newborn piglets and causing massive economic losses to the pig industry. The entry of PEDV into cells is mediated by the binding of its spike protein (S protein) to a host cell receptor. Here, we review the structure of PEDV, its strains, and the structure and function of the S protein shared by coronaviruses, and summarize the progress of research on possible host cell receptors since the discovery of PEDV.