Herpes
Vincenzo Berghella in Maternal-Fetal Evidence Based Guidelines, 2022
Over 90% of HSV episodes in pregnancy are either recurrent or nonprimary first-episode HSV. Intimate contact between a susceptible person (without antibodies against the virus) and an individual who is actively shedding the virus, or with body fluids containing the virus is required for HSV infection to occur. Contact must involve mucous membranes or open or abraded skin. HSV invades and replicates in neurons as well as in epidermal and dermal cells. Virions travel from the initial site of infection on the skin or mucosa to the sensory dorsal root ganglion, where latency is established. Viral replication in the sensory ganglia leads to recurrent clinical outbreaks. These outbreaks can be induced by various stimuli, such as trauma, ultraviolet radiation, extremes in temperature, stress, immunosuppression, or hormonal fluctuations. Viral shedding, leading to possible transmission, occurs during primary infection, during subsequent recurrences, and during periods of asymptomatic viral shedding.
Identifying Airborne Transmission as the Dominant Route for the Spread of COVID-19
William C. Cockerham, Geoffrey B. Cockerham in The COVID-19 Reader, 2020
Several parameters likely influence the microorganism survival and delivery in air, including temperature, humidity, microbial resistance to external physical and biological stresses, and solar ultraviolet (UV) radiation (7). Transmission and infectivity of airborne viruses are also dependent on the size and number concentration of inhaled aerosols, which regulate the amount (dose) and pattern for respiratory deposition. With typical nasal breathing (i.e., at a velocity of –1 m·s−1) (4), inhalation of airborne viruses leads to direct and continuous deposition into the human respiratory tract. In particular, fine aerosols (i.e., particulate matter smaller than 2.5 μm, or PM2.5) penetrate deeply into the respiratory tract and even reach other vital organs (14, 15). In addition, viral shedding is dependent on the stages of infection and varies between symptomatic and asymptomatic carriers. A recent finding (16) showed that the highest viral load in the upper respiratory tract occurs at the symptom onset, suggesting the peak of infectiousness on or before the symptom onset and substantial asymptomatic transmission for SARS-CoV-2.
Diagnosing Viral Infections
Firza Alexander Gronthoud in Practical Clinical Microbiology and Infectious Diseases, 2020
Depending on the stage of infection, viruses can be directly found in bodily fluids such as blood, urine, respiratory secretions, stool and CSF by using molecular tests aimed at detecting viral DNA or RNA. Viruses can be transmitted to the environment and people via shedding in urine, stool and respiratory secretions. Viral shedding can occur before symptoms develop until even after the infection has been resolved and the individual is asymptomatic. Immunocompromised individuals can shed the virus for a longer time than immunocompetent individuals. Viruses which cause latent infections can intermittently reactivate during life and be shed in bodily fluids. This may or may not cause any symptoms. Knowledge of shedding and transmission of viruses helps determine the type and duration of infection control precautions to use.
Microsurgery in the era of COVID-19
Published in Baylor University Medical Center Proceedings, 2021
Jesse I. Payton, Stacy Wong, Nicholas F. Lombana, Michel S. Saint-Cyr, Andrew M. Altman, Sebastian M. Brooke
Transmission of COVID-19 occurs through droplets and contact. Droplets spread 1 to 2 meters and infect mucous membranes.3,4 Certain operations and techniques aerosolize the virus, potentiating transmission at greater distances.5 The incubation period ranges from 1 to 14 days, with a median of 3 to 7 days, and patients are infectious during this time.3,4,6 Viral shedding is known to have occurred from 4 to 37 days.7,8 The most common symptoms are fever, cough, ageusia, anosmia, expectoration, myalgia or fatigue, and shortness of breath.4,9,10 However, 8.3% to 58.3% of patients remain asymptomatic based on two studies in Japan looking at evacuees from Wuhan and patients from the Diamond Princess cruise ship.11,12
Clinical course of SARS-CoV-2 infection in patients with severe acquired brain injury and a disorder of consciousness: an observational study
Published in Brain Injury, 2021
Antonio Caronni, Emanuele Liaci, Anna Bianchi, Alessandro Viganò, Francesco Marenco, Angela Comanducci, Daniela Maria Cabrini, Mario Meloni, Margherita Alberoni, Elisabetta Farina, Mariangela Bianco, Silvia Galeri, Guya Devalle, Jorge Navarro
Another interesting finding seems the clearance time of SARS-CoV-2, which was on median more than 50 days, i.e. longer than usually reported. Viral load in throat swabs progressively decreases after symptoms onset and reaches the detection limit after about three weeks (42). Even if a median shedding time of about 21 days has been reported by different Authors (43), prolonged viral shedding has been reported as well with isolated cases showing detectable levels of the virus up to 47 days (44). Note that even when this very long threshold is applied, three of the six positive patients would be considered prolonged shedders. Longer times to negative test seem in line with the view according to which patients with SABI have a weak immune response to SARS-CoV-2. Under this hypothesis, patients with SABI could be weak in eradicating the virus, eventually becoming long-term carriers.
Prolonged SARS-CoV-2 detection and reversed RT-PCR results in mild or asymptomatic patients
Published in Infectious Diseases, 2021
Sung-min Kim, Yoon Jin Hwang, Youngseok Kwak
Several months after Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) was recognised in China, it is now pandemic. Global efforts are being made to stop the growing number of coronavirus disease 2019 (COVID-19) patients, but information about this novel coronavirus is still lacking. Moreover, due to the rapid increase in the number of patients, treatment and research have been focussed on severe patients, and studies on mild or asymptomatic patients have been insufficient. However, there are many reports that the transmission of SARS-CoV-2 also occurs in mild or asymptomatic patients [1–7]. Mild or asymptomatic patients may produce greater transmission due to increased mobility and reduced disease awareness. Therefore, it is important to know the clinical course and duration of viral shedding in mild or asymptomatic patients. However, although accurate details are still unknown, the sensitivity of upper respiratory specimens to detect SARS-CoV-2 seems to be low [8–10]. This adds confusion when deciding a clinical course or when to de-isolate mild or asymptomatic COVID-19 patients [11]. We experienced many negative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) results that turned positive the next day during management of mild or asymptomatic patients. Therefore, in a cohort of patients with mild or no symptoms at an isolation facility, we evaluated the proportion of patients with prolonged (>3 weeks) SARS-CoV-2 RT-PCR positivity. Additionally, we analysed the rate at which negative RT-PCR results reversed to positive or indeterminate results.
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