Hand, Foot And Mouth Disease

Description of the Microorganism
A particular subset of enteroviruses known as picornavirus is what causes the illness.
They are small, non-enveloped, and have a single-stranded, positive-sense RNA genome.
Coxsackievirus A16 and enterovirus 71 are the principal causes of HFMD. In terms of size, these
viruses are icosahedral and range from approximately 22 to 30 nanometers. (Noisumdaeng, et
al., 2019). These viruses can be seen under a light microscope and appear like tiny, rounded
particles.
From the viewpoint of morphology, Coxsackievirus A16 and Enterovirus 71 have a
simple structure in which they encapsulate the genomic RNA into a coat. Four structural proteins
forming the capsid structure are an initial barrier to prevent viral attachment to the host cells.
These viruses have no grammatical reactions or cellular structures because they are obligatory
intracellular parasites.
Electron microscopy is irreplaceable in its capacity to depict these microorganisms. An
electron microscope is a powerful tool that provides high resolutions for up-close examination of
viral morphology. However, other staining techniques, such as immunological fluorescence
labeling, can boost contrast and make virus particles easier to see (Kamau, et al., 2021). It is
critical to understand the microscopic characteristics of these enteroviruses for both diagnostic
purposes and the development of antiviral treatments.
Virulence Factors

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Certain virulence factors allow the primary etiologic agents of HFMD, namely,
Coxsackie virus A16 and enterovirus 71, to undergo pathogenesis. Their ability to bind to
particular receptors in the mucosal epithelium lining at the mouth is one of the critical
considerations. The viral capsid protein, particularly the vp1 protein, affects this attachment.
After adhering, the virus invades the host cells, which subsequently experience multiplication of
the virus, resulting in the specific plaques seen with HFMD (Zhu et al., 2023). In addition, these
enteroviruses have ways of avoiding host immunity. One example is that they can suppress their
host's interferon, making producing such defenses difficult. It promotes an effective penetration
into the host cell by the virus, worsens the course of HFMD manifestations in those who are sick,
and, therefore, constitutes one more mechanism of immune evasion strategy.
Immunity
The host defenses against Coxsackievirus A16 and Enterovirus 71 mainly rely on innate
and adaptive immunity. Innate immunity is a primary barrier, comprising mucosal barriers,
phagocytic cells, and interferons. An essential part of the process involves the adaptive immune
system, which includes both the humoral response (using antibodies) and the cellular response
(by T cells). Such specific antibodies direct their attacks against viral proteins, especially those at
the viral surface level that can interdict more infections (Ling et al., 2019). Specifically, T-cell
responses are critical in identifying and killing contaminated cells. The immune response is
usually adequate, but viruses can escape some components of the host defense system, which
allows several chronic or life-threatening pathologies, particularly when the host's defense
system is weakened.
Infectious disease information

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Coxsackievirus A16 and Enterovirus 71 are typically the causes of hand, foot, and mouth
disease, which has skin lesions on the face, mouth, and hands as its most prevalent symptoms
(but occasionally also affects the kidneys, heart, or lungs). This is characterized by vesicles on
the hands, feet, and oral cavity, which are the hallmarks of HFMD. However, severe HFMD has
possible complications like viral meningitis, encephalitis, and myocarditis, which are extremely
dangerous in young children. Despite having an acute infection, complications may lead to
chronic sequelae (Hooi et al., 2020). Although systemic involvement of the integumentary and
nervous systems is the primary cause, systemic spread is also likely to affect other body organs,
thus indicating the numerous organ tropisms.
Epidemiology
Most of the time, Coxsackievirus A16 and Enterovirus 71 are spread through the fecal-
oral and oral-oral routes. However, fomites and respiratory secretions can also be contaminated
and act as pathways of transmission. Infected individuals act as reservoirs for the viruses,
especially children, who are significant carriers. The persistent infection in the environment is
primarily associated with fecal-oral transmission, water, and infected surfaces (Yin et al.