The emergence and spread of infectious diseases with pandemic potential occurred regularly throughout history. Major pandemics and epidemics such as plague, cholera, flu, severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) have already afflicted humanity. The world is now facing the new coronavirus disease 2019 (COVID-19) pandemic. Many infectious diseases leading to pandemics are caused by zoonotic pathogens that were transmitted to humans due to increased contacts with animals through breeding, hunting and global trade activities. The understanding of the mechanisms of transmission of pathogens to humans allowed the establishment of methods to prevent and control infections. During centuries, implementation of public health measures such as isolation, quarantine and border control helped to contain the spread of infectious diseases and maintain the structure of the society. In the absence of pharmaceutical interventions, these containment methods have still been used nowadays to control COVID-19 pandemic. Global surveillance programs of water-borne pathogens, vector-borne diseases and zoonotic spillovers at the animal-human interface are of prime importance to rapidly detect the emergence of infectious threats. Novel technologies for rapid diagnostic testing, contact tracing, drug repurposing, biomarkers of disease severity as well as new platforms for the development and production of vaccines are needed for an effective response in case of pandemics.

Viral Interference between Respiratory Viruses

Herpes simplex virus 1 (HSV-1) can be responsible for life-threatening HSV encephalitis (HSE). The mortality rate of patients with HSE who do not receive antiviral treatment is 70%, with most survivors suffering from permanent neurological sequelae. The use of intravenous acyclovir together with improved diagnostic technologies such as PCR and magnetic resonance imaging has resulted in a reduction in the mortality rate to close to 20%. However, 70% of surviving patients still do not recover complete neurological functions.

Insect males of several parasitoid species have limited amount of sperm at emergence and experience sperm depletion when mate acquisition rate is high, suggesting that sperm production and storage could be a limiting factor for male's fitness. Sperm-depleted males of the parasitoid wasp Trichogramma evanescens continue to mate, and the impact of this behavior on sperm storage by females has been studied. Virgin females T. evanescens stored 50.6 ± 13.1 (Mean ± SD) sperm when mating first with a virgin male. However, when these females mated first with a sperm-depleted male and then with a virgin male, they stored only 18.9 ± 7.8 sperm, indicating that mating with a sperm-depleted male has a cost and limits sperm acquisition from fertile males. Following a mating with a sperm-depleted male, females had to mate with three virgin males to restore their sperm supply confirming that additional mating enabled the female to store a limited number of sperm. According to our results, by continuing to mate, sperm-depleted males do not prevent mates from copulating again but they decrease their ability to store other male's sperm. Continuing to mate could be a strategy to increase the relative fitness of sperm-depleted males.