This episode explores hand, foot, and mouth disease, including its various viruses, symptoms, outbreaks, and potential vaccines. The hosts share personal experiences and knowledge, discuss enteroviruses and echo viruses, treatment options, the origins and global spread of the disease, and the vast world of viruses. They also explore hypotheses about virus origins and express gratitude to listeners.
Hand-foot-and-mouth disease is a common viral infection primarily affecting children under the age of five, causing symptoms such as fever, sore throat, rash on hands, feet, and buttocks, and rarely leading to severe complications.
The origin of viruses is still debated, with three main hypotheses: virus-first, escape, and reduction, and more research is needed for a definite conclusion.
Endogenous retroviruses (ERVs) are genetic sequences derived from ancient viruses that exist in the genomes of cells, playing roles in gene regulation and providing insights into the relationship between viruses and host genomes.
Deep dives
Hand-foot-and-mouth disease: Overview
Hand-foot-and-mouth disease (HFMD) is a common viral infection that primarily affects children under the age of five. It is caused by enteroviruses, with the most common culprits being coxsackievirus A16 and enterovirus 71. HFMD typically begins with a fever, sore throat, and general malaise, followed by the emergence of a rash on the hands, feet, and buttocks. The rash starts as red spots and progresses to fluid-filled blisters. While HFMD is usually self-limiting and causes mild symptoms, it can rarely lead to severe complications, such as neurologic manifestations or even death. It is highly contagious and spreads through direct contact with infected individuals or contaminated objects. The incubation period is usually three to five days, and the disease resolves within a week to ten days. Symptomatic treatment and supportive care are the main management approaches for this disease.
Viruses and the Origin of Life
The origin of viruses is still a topic of scientific debate. There are three main hypotheses: virus-first, escape, and reduction. The virus-first hypothesis suggests that viruses emerged before cells and originated from a soup of RNA molecules. They evolved to infect cells once cells existed. This hypothesis is supported by the existence of RNA viruses and genetic sequences found only in viruses. The escape hypothesis proposes that viruses derived from cells. It suggests that genetic elements called retrotransposons, found in cell genomes, moved around and eventually gave rise to viruses. The reduction hypothesis suggests that viruses are remnants of cellular organisms that became simplified over time. Some hybrid hypotheses also incorporate aspects of these three main hypotheses. More research is needed to reach a definitive conclusion on the origin of viruses.
Endogenous Retroviruses and Viral Impact on Genomes
Endogenous retroviruses (ERVs) are genetic sequences derived from ancient viruses that became incorporated into the genomes of cells. ERVs make up a significant portion of the human genome, estimated to be around 8%. While most ERVs are inactive and do not code for any functional proteins, some still have an impact, playing roles in gene regulation and placental development. ERVs can provide insight into the evolutionary relationships between different animal species and the history of viruses. By comparing shared viral genes across species, scientists can gain a better understanding of ancient viral infections and their effects on host evolution. The existence of ERVs underscores the intricate relationship between viruses and the genomes of their hosts.
Cocksacki Virus A6: Severe Skin Manifestations and Widespread Involvement
Cocksacki Virus A6 is a highly infectious virus causing severe skin manifestations that are more widespread and severe than those seen in other Cocksacki Virus infections. It has been spreading globally since 2008, causing outbreaks with symptoms such as large blisters, deep blistering eruptions, widespread and very itchy rashes, and nail loss. This virus is an exception as most adults do not show symptoms even if infected. The reasons for the increased virulence of Cocksacki Virus A6 are not completely understood, but it may be related to differences in virulence factors and host factors.
Enterovirus 71: Severe Neurologic Manifestations and Global Distribution
Enterovirus 71, while globally distributed, causes the largest and most severe epidemics in Asia and can result in severe neurologic manifestations. It is one of the viruses that can cause hand-foot-and-mouth disease and is associated with outbreaks that involve never-before-seen case numbers and new symptoms. The exact reasons for its virulence and the drivers behind the increase in outbreaks are not fully understood. However, research suggests that host factors and differences in the way individuals respond to the virus may play a role. The development of effective vaccines and ongoing research on prevention and changing epidemiology are areas of focus in managing hand-foot-and-mouth disease.
Hand, foot, and mouth disease (HFMD). The dreaded scourge of daycares, kindergartens, even occasionally college campuses, and the topic of this week’s episode. From the multiple viruses that cause HFMD to the wide array of symptoms (bye bye, fingernails), from the relatively recent discovery of this disease to the ancient origins of all viruses (deep time, y’all), from the changing nature of outbreaks to the development of potential vaccines (fingers crossed) - in this episode we’re going way beyond the basics of hand, foot, and mouth disease. Whether or not you’ve had the pleasure of being up close and personal with this disease, this episode is sure to leave you slightly horrified/mildly impressed by the infectiousness, longevity, resilience, and deep roots of the HFMD viruses.
