Preface

Streptococci are facultatively anaerobic Gram-positive bacteria that are isolated in large numbers from most human body sites. They are common colonizers of the mucosae. The border between pathogenic and non-pathogenic streptococcal species is often indistinct. Many pathogenic streptococci, such as *Streptococcus pneumoniae*, *Streptococcus pyogenes* may asymptomatically colonize the nasopharynx of healthy people and become a source of endogenous infection under favorable conditions. Streptococcal infection is a complex multi-stage process involving, on the one hand, a host with an array of protective mechanisms of defense, and bacteria with virulence factors that neutralize the above mentioned mechanisms (envelopes, enzymes, toxins, and superantigens) on the other. The predominance of one side or another is reflected by the elimination of the bacteria or infection, either symptomatic or limited to asymptomatic carriage. The clinical course and severity of infection vary greatly among infecting streptococcal strains. Effective ways to prevent both asymptomatic streptococcal colonization and infection, which include vaccination, are constantly demanded.

The Bacterial Infectious Diseases topic features two chapters this year and we look forward to more in the next.

**Katarzyna Garbacz and Tomas Jarzembowski**

Medical University of Gdańsk, Gdańsk, Poland Topic Editors: Bacterial Infectious Diseases

The Fungal Infectious Diseases topic highlights two chapters, the first titled Talaromyces marneffei *Infection: Virulence Factors and Rapid Diagnostics* and the second one titled *Evolution of Parasitism and Pathogenic Adaptations in Certain Medically Important Fungi*. In this first year of its existence, after the topic structure has been introduced, perhaps this is not much but it will, all in all, contribute to this topic's relevance and hopefully open new possible research paths for further novel developments in this particular area which will be welcomed.

> **Yuping Ran** Sichuan University, Chengdu, China Topic Editor: Fungal Infectious Diseases

Parasitic diseases have evolved alongside their human hosts. In many cases, these diseases have adapted so well that they have developed efficient resilience methods in the human host and can live in the host for years. In the current atmosphere of the Coronavirus pandemic, communities around the world, particularly those in different underdeveloped areas, are faced with the growing challenges of the high burden of parasitic diseases which should not be neglected in this context.

Therefore, we need to revisit certain topics in this particular field of research with fresh findings and new perspectives. All researchers are invited to actively participate in this open call.

### **Amidou Samie**

University of Venda, Thohoyandou, South Africa Topic Editor: Parasitic Infectious Diseases

The discovery of viruses dates back to around 3700 BC, when the first written record of virus infection was immortalized through representation in Egyptian hieroglyphs, depicting the classical signs of poliomyelitis and smallpox infection. However, the struggle of the human brain with these microbes is still fresh and unanswered. The scientific studies of viruses began in the late 19th century when their existence was documented and the term "virus" was coined. By mid-20th century, almost 2,000 recognized species of animal, plant, and bacterial viruses had been discovered. Despite several achievements over the past years in virology, viruses still continue to pose bigger, new, and fatal threats to the world's populations which poses several challenges to virologists all over the world. Several viral infections that may be fatal or debilitating threaten the human race. The majority of viral diseases attack infants and young children, while others strike people in their prime. There is a continual trend of extreme variation in viral epidemics considering their extent, severity, duration, appearance, reappearance, and the emergence of new diseases.

However, as we develop newer techniques, the viruses are getting smarter, and their advances and abilities to adapt and resist are posing greater challenges to virologists all over the world. The pattern and profile of viral infections are undergoing several changes that make them hard to analyze. Recent outbreaks and resurgence of highly pathogenic viruses continue to dominate the disease incidence rates globally. The need of the hour is to win over the virus, which is not a one step phenomenon; instead, it is a chained and linked process between individuals, researchers, analysts, antiviral drug developers, the government, and the public. However, the effort of opening several hundreds of new labs is appreciated, but viral research needs an upgrade which may be fulfilled by building capacity at various levels. There is an urgent need for learned and trained human resources in virology. Therefore, specialized virology programs should be included at various institutes/universities, as well as medical courses for clinical/medical/basic microbiologists and paramedical staff, to train them in differential and molecular diagnostics/antiviral drug research, etc. In spite of accurate diagnostics, the lack of specific antiviral drugs and vaccines is

a major concern, through which emerging, reemerging, and drug-resistant viruses pose the foremost threat. Therefore, there is a desperate need for the development of effective antivirals and vaccine strategies. We should consider another challenging and emerging clinical area of personalized medicines, due to differences in host genetic factors and viral strain variation when compared to foreign countries. A viral outbreak forecast system which can predict viral epidemics/pandemics based on intensive research and molecular biomarkers could be developed, potentially saving thousands of lives nationwide.

The aim of this topic is to collect a comprehensive overview of recent research trends and discoveries in various viral infectious diseases emerging around the globe. The emergence of any viral disease is hard to anticipate, which often contributes to death rates. A viral disease can be defined as an infectious disease that has recently emerged in a population or that exists in nature with a rapid increase in incidence or a geographic range. This topic's aim is to publish work focused on various crucial factors related to emerging viral infectious diseases, including epidemiology, pathogenesis, host immune response, clinical manifestations, diagnosis, treatment, and clinical recommendations for managing viral infectious diseases, highlighting the recent issues with future directions for effective therapeutic strategies.

I am overwhelmed in all humbleness and gratefulness to acknowledge my depth to all the contributors who trusted me and supported me in this work. My research fellows are the motivating force behind anything constructive that I do and a center of my research and academic work. I would like to express my special thanks of gratitude to my mentors, teachers, and students. Also, I would like to thank my colleagues, family, and friends who gave a lot of encouragement and support during the work on this topic. A happy environment at home is essential for any kind of growth, and I thank my family, especially my wife and children for the same.

### **Shailendra K. Saxena**

King George's Medical University, Lucknow, India Topic Editor: Viral Infectious Diseases

Section 1
