key: cord-0923585-6zf3ko6x
authors: Craviotto, Vincenzo; Furfaro, Federica; Loy, Laura; Zilli, Alessandra; Peyrin-Biroulet, Laurent; Fiorino, Gionata; Danese, Silvio; Allocca, Mariangela
title: Viral infections in inflammatory bowel disease: Tips and tricks for correct management
date: 2021-07-21
journal: World J Gastroenterol
DOI: 10.3748/wjg.v27.i27.4276
sha: 3a9e50845d6248e560eed4117eeced6253ee0cc2
doc_id: 923585
cord_uid: 6zf3ko6x

Over the past decades, the treatment of inflammatory bowel diseases (IBD) has become more targeted, anticipating the use of immune-modifying therapies at an earlier stage. This top-down approach has been correlated with favorable short and long-term outcomes, but it has also brought with it concerns regarding potential infectious complications. This large IBD population treated with immune-modifying therapies, especially if combined, has an increased risk of severe infections, including opportunistic infections that are sustained by viral, bacterial, parasitic, and fungal agents. Viral infections have emerged as a focal safety concern in patients with IBD, representing a challenge for the clinician: they are often difficult to diagnose and are associated with significant morbidity and mortality. The first step is to improve effective preventive strategies, such as applying vaccination protocols, adopt adequate prophylaxis and educate patients about potential risk factors. Since viral infections in immunosuppressed patients may present atypical signs and symptoms, the challenges for the gastroenterologist are to suspect, recognize and diagnose such complications. Appropriate treatment of common viral infections allows us to minimize their impact on disease outcomes and patients’ lives. This practical review supports this standard of care to improve knowledge in this subject area.

Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC) are lifetime conditions characterized by a relapsing and remitting clinical course. The complete pathogenic mechanisms of IBD are unknown. The major hypothesis is that the diseases occur when genetically vulnerable individuals meet unknown environmental triggers that exacerbate an inappropriate immune response against gut microbiota [1] . Curative therapies for IBD are not available yet. Medical treatment aims to guarantee long-lasting disease remission, thus avoiding complications and improving patient quality of life.

Drugs currently available for the management of IBD are mesalazine (5-ASA), locally active steroids, systemic steroids, thiopurines such as azathioprine (AZA) and mercaptopurine (MP), methotrexate (MTX), and biological therapies [Tumor necrosis factor-alpha inhibitors (anti-TNF) and other monoclonal antibodies targeting interleukin 12 (IL-12), IL-23, and cellular adhesion molecule ligands a4 integrin and a4b7 integrin] [2] .

Over the past decades, IBD treatment has become more targeted, anticipating the use of immune-modifying therapies at an earlier stage [3, 4] . This has been correlated with favorable prognosis such as a reduction in surgery, hospitalization, and use of steroids[5-10], but it has also brought with it concerns about potential infectious complications.

IBD patients treated with immune-modifying therapies have an increased risk of developing severe infections, including opportunistic infections sustained by viral, bacterial, parasitic, and fungal agents [11] [12] [13] [14] [15] [16] , that are associated with hospital admission, use of intravenous antimicrobials, disability and death. The incidence of serious infections is not well defined, ranging from 10 to 100 events per 1000 patientyears [13, [17] [18] [19] . Opportunistic infections are caused by ordinarily nonpathogenic organisms that can take advantage of an impaired immune system. According to the European Crohn's and Colitis Organization (ECCO) consensus guidelines on the prevention, diagnosis and management of opportunistic infections in IBD [20] , updated in 2014 [12] , IBD patients treated with immune-modifying agents, especially in combination, those with malnutrition, comorbidities and a history of severe infections should be considered at risk for opportunistic infections. In an era of intensifying immune-modifying therapies, infective complications have emerged as a focal safety concern in patients with IBD. Today's challenge for gastroenterologists is to adopt preventative strategies, suspect, recognize, and treat appropriately IBD infectious complications to minimize their impact on disease outcomes and patients' lives. In particular, viral infections represent demanding problems for the clinician, as they are often difficult to diagnose and are associated with significant morbidity. This review intends to outline the most relevant viral infections in IBD, focusing on the careful S-Editor: Gong ZM L-Editor: Webster JR P-Editor: Xing YX screening and monitoring before and during the use of immune-modifying therapies, timing of vaccinations, opportunity for primary or secondary prophylaxis and indications for therapy. A summary of recommendations for the prevention and management of viral infections in IBD are shown in Table 1 .

A population-based study of patients with IBD [18] found that of opportunistic infections, 40% were due to viral pathogens. A recent prospective observational study [21] estimated that the incidence rate of systemic viral infections in patients with IBD was 2 per 1000 person-years, three-fold higher compared to the general population. Age is an independent risk factor for opportunistic infections in IBD [22] , but for viral infections, the highest incidence rates are observed in patients under the age of 35 years [21] . In elderly patients, infections sustained by viral pathogens are rare compared with the younger population[23], except for influenza [24] , herpes zoster reactivation (shingles) [25] , and viral gastroenteritis [26] . Viral infections may also be triggered by disease activity and the resulting defective mucosal immunity, especially cytomegalovirus (CMV) colitis [27, 28] , and Epstein-Barr virus (EBV) systemic reactivation [29] . Finally, viral infections may arise as adverse events attributable to the immune-modifier action of IBD drugs. The direct correlation between a specific immunomodulator or biologic drug and viral infections has not been established. A retrospective analysis found that AZA/6MP-treated patients are at risk of developing opportunistic viral infections, such as herpes simplex (HSV), varicella-zoster (VZV), CMV, and EBV [11] . In a prospective cohort of outpatients with IBD, it was reported that exposure to thiopurines was associated with an increased incidence of cutaneous herpes flares and warts [30] . The incidence of zoster is increased in patients with IBD [31-33] and exposure to immunomodulators, in particular corticosteroids or combination therapy with thiopurines and anti-TNF agents, raises the risk[18,34]. During a 5-year follow-up, combination therapy (anti-TNF + thiopurine) was associated with an increased risk of opportunistic viral infections compared to anti-TNF monotherapy (1.3% vs 0.7%); no difference was found compared to thiopurine monotherapy (1.1%). Conversely, anti-TNF monotherapy was associated with a decreased risk of opportunistic viral infection compared to thiopurine monotherapy, suggesting that thiopurines drive the risk of opportunistic viral infections under combination therapy. These observations seem to agree with the AZA/6MP mechanism of action which primarily suppresses T lymphocytes activity that is involved in the prevention of viral infections.

With regard to corticosteroids, it is difficult to conclude their benefit and risk as they have many selection biases, as they are likely to be given to patients with severe disease, and there is heterogeneity in the type, dose and duration of their use. There are data suggesting that doses of prednisolone above 20 mg are associated with increased risk of bacterial and viral infections in IBD [35] . In patients with IBD exposed to thiopurines and anti-TNF agents, the increase in mortality from infection is negligible [17, 36] , instead, some studies have reported increased mortality in patients exposed to corticosteroids [34, 37] . Case series recorded thiopurine-associated fatal infections, mainly in young patients. These infections include severe forms of varicella [38] and primary EBV or CMV infections complicated by hemophagocytic lymphohistiocytosis[39,40].

In immunocompromised patients, fever is sometimes the only manifestation of severe infection [41] . The approach in febrile patients must include exploration of their history and accurate physical examination. It is essential to recognize any symptoms or signs that can help identify the site of infection. Evaluation tests should include complete blood cell counts, C-reactive protein, serum procalcitonin (PCT), urine analysis and culture, VZV serology in patients without a reliable history of varicella immunization, hepatitis B virus (HBV) and hepatitis C virus (HCV), EBV and human immunodeficiency virus (HIV) serologies, stool examinations and strongyloidiasis serology (for returning travelers) and chest X-ray [12] . In the case of severe illness or when unusual pathogens are suspected, an infectious disease specialist should be involved.

In patients with respiratory symptoms (dyspnea, cough, purulent sputum, hemoptysis, pleuritic chest pain) or focal chest signs, a chest X-ray or chest ultrasound should be performed, and oxygen saturation determined. For patients with abnormal Dermatological manifestations of viral infections are mainly caused by HSV and VZV. The diagnosis of these conditions is usually based on clinical manifestations. Yet virological analysis can be performed directly on a recent lesion by PCR.

Diagnostic approaches for IBD patients with infectious symptoms are shown in Table 2 .

IBD patients should follow all age-appropriate vaccinations as recommended by the Advisory Committee on Immunization Practices [46] . It is also important to respect the optimal timing of vaccination with regard to initiation of immunosuppressive therapy, as the use of immunosuppressive agents can lead to decreased immunogenicity of the vaccination [47, 48] .

In the case of minor infection (rhinitis, upper respiratory tract infection, etc.) with no risk of disseminated disease or rapid worsening, it is unnecessary to withdraw immunomodulators. However, in the case of risk for disseminated or uncontrolled disease (shingles, viral pneumonia, encephalitis), high-grade fever and infection with a well-known mortality risk, withdrawal of immunomodulators are best advised at the peak of infection, and the decision to resume immunomodulator treatment is on a case-by-case basis and a multidisciplinary approach[49].

Hepatitis A virus (HAV) is responsible for hepatitis A infection, which is usually a mild, self-limited disease that does not become chronic. It is transmitted by the fecaloral route, and poor hygienic and socioeconomic conditions promote this infection [50, 51] . Infection confers lifelong immunity and is preventable via vaccination. The onset of symptoms is sudden, with malaise, asthenia, nausea, vomiting, and pain in the upper abdominal quadrants. No specific disease manifestations in immunocompromised hosts have been described. The most relevant biochemical alteration is the increase in transaminases (often > 1000 IU/dL) and, generally, precedes the increase in bilirubin (typically ≤ 10 mg/dL). The presence of IgM anti-HAV antibodies allows the etiological diagnosis. The American College of Gastroenterology and the Korean Association for the Study of Intestinal Diseases recommend a test for HAV (IgG anti-HAV antibodies) in patients with IBD. In those who are negative, vaccination should be recommended [52, 53] . On the other hand, ECCO guidelines suggest vaccination only in high-risk subjects and those traveling to endemic areas [12] . Inactivated hepatitis A vaccines should be preferred[54], as they have high, long-lasting immunogenicity with few side effects[55]. Since immunosuppressive therapy can lower the seroconversion rate[56], optimal timing for HAV vaccination is at IBD diagnosis or before starting immunosuppressive therapy, even if administration is acceptable during maintenance therapy. The vaccine should be administered in 2 doses with an interval of 6 mo.

The global HCV prevalence is estimated at 2.5%, ranging from 2.9% in Africa and 1.3% in the Americas[57]. In Europe it is estimated that 0.2-2% of the population is infected with HCV. The prevalence of HCV in patients with IBD is comparable to that in the general population[58-61]. HCV is typically transmitted parenterally. Acute HCV infection is often asymptomatic and chronic HCV infection develops in about 85% of all cases. Among patients with chronic HCV infection, 20% develop liver cirrhosis within 20 years of disease duration, with a high rate of incidence of hepatocellular carcinoma. General measures to reduce or prevent HCV infection are appropriate since vaccination and prophylactic treatment are not available. The ECCO guidelines suggest performing HCV screening before starting treatment with immune-modifying drugs for IBD. , possibly before starting biologics or immunomodulator therapy. However, the timing strategy for treating HCV-infected IBD subjects could depend on several factors, including the IBD activity and patient's comorbidities. If HCV-infected patients with IBD cannot delay their immunemodifying therapy, their liver function should be monitored closely. There are no data to suggest that biologics are associated with reactivation or exacerbation of the course 

Human papillomavirus (HPV) is a sexually transmitted infection. There are approximately 40 serotypes of HPV classified into low-risk serotypes and high-risk serotypes, which are associated with cervical and anal squamous cell carcinoma [86] . HPV also causes cutaneous warts. There are reports of an increased frequency of HPV-related anogenital warts in patients receiving AZA[30], but not anti-TNF[87]. IBD has not been associated with the development of cervical cancer; however, patients with CD who smoke, are younger at diagnosis, and those who use thiopurines or methotrexate combined with corticosteroids might be more at risk [88, 89] . Other immunosuppressive medications, in particular anti-TNF therapy, seem not to have an increased risk. However, the quality of evidence is poor, physician awareness and prevention by lifestyle counseling, HPV vaccination and screening are warranted [90] . There are three types of HPV vaccine: bivalent, Cervarix, comprising 16, 18 serotypes, quadrivalent, Silagard, and Gardasil, with 6, 11, 16, 18 serotypes, and nine-valent, Gardasil 9, with 6, 11, 16, 18, 31, 33, 45, 52, 58 serotypes. As the HPV vaccines do not contain live viruses, they may be administered to an immunosuppressed patient with an excellent safety profile and immunogenicity [91] . The vaccine is indicated for women aged 9 to 26 years, preferably before the first sexual intercourse but also after initiation of sexual activity. Male patients should be vaccinated at the age of 11 to 12 years, and catch-up for those aged 13 to 21 years. Of note, cervical screening recommendations are similar for vaccinated and nonvaccinated women. In IBD patients, a cervical smear test should July 

HSV type 1 (HSV-1) and HSV type 2 (HSV-2) are common infections worldwide. HSV-1 is implicated in most cases of orofacial herpes lesions ("cold sores"), while HSV-2 causes most cases of recurrent genital herpes [116] . After primary infection, HSV establishes chronic infection in neural ganglia and reactivates on mucosa and skin; [150, 151] than non-infected patients. Colonic CMV infection can be diagnosed by hematoxylin and eosin (H&E) or immunohistochemical staining (IHC) histology, serology assay, polymerase chain reaction (PCR) for CMV DNA in peripheral blood or tissue (from targeted biopsies taken from the ulcer base), and CMV antigenemia (pp65) [152] . The gold standard for diagnosing CMV overinfection is the identification of CMV inclusions (typically basophilic intranuclear inclusions) or positive CMV-specific immunohistochemistry staining on histopathology [153] , eventually followed by tissue-direct PCR for viral load quantification. CMV infection cannot be excluded based on a negative whole-blood PCR result [154] . In patients who are steroid-dependent or refractory [155] and those with high CMV viral load in colonic tissue [156] , antiviral therapy is recommended. Several agents are available for CMV infection, including ganciclovir, valganciclovir and foscarnet. The most used antiviral agent is intravenous ganciclovir at a dose of 5-7.5 mg/kg twice daily for 2 wk [152] . ECCO guidelines allow a course of intravenous ganciclovir 5 mg/kg twice for 3-5 days, followed by oral valganciclovir at 900 mg per os twice daily for 2-3 wk[12]. Foscarnet (for 2-3 wk) is an alternative in case of resistance or intolerance (hematologic or renal toxicity). Overall, there is a lack of knowledge to give recommendations on managing immunosuppressant medications during or after treatment of CMV colitis. Inducing remission with anti-TNF and tapering off the steroids while continuing intravenous ganciclovir may be an acceptable strategy [152] .

VZV causes varicella (chickenpox) during its primary infection, and after decades of latency in sensory ganglia, it maintains the potential for reactivation as herpes zoster (shingles). Primary infection is generally a mild-moderate disease in most children. However, it can be life-threatening in adults (especially during pregnancy) and immunocompromised patients, potentially leading to severe complications such as central nervous system involvement, pneumonia, secondary bacterial infections, and death [157] . At diagnosis, all IBD patients (unless those with documented vaccination history) should be tested for VZV IgG serology [158] . Corticosteroids, thiopurines, methotrexate, and anti-TNF in monotherapy or even more in combination, are recognized risk factors for varicella infection [159, 160] . The literature describes 23 cases of varicella in IBD patients receiving immunosuppressants and the fatality rate is reported to be 22% [161] . Diagnosis is based on clinical signs (fever and typical vesicular lesions in different stages of development on the face, trunk, and extremities), or real-time PCR on samples taken from skin lesions in an immunocompromised host or in the evaluation of atypical lesions [162] . In immunocompromised hosts with active varicella lesions, antiviral therapy is recommended in order to reduce the severity of symptoms and the risk of serious complications. Oral valacyclovir (1 g 3 times daily) may be considered in patients with mild disease followed closely. For most patients, initial therapy with intravenous acyclovir (10 mg/kg every 8 h) is suggested, with the possibility of switching to oral antiviral after defervescence in the absence of visceral involvement. The treatment duration is 7-10 days, and it has to be continued until all lesions have crusted. After significant exposure, primary prophylaxis with VZV immune globulin within 10 days is indicated in IBD patients receiving immunosuppressive therapy since they are ineligible for varicella vaccine prophylaxis [163] . From a prevention perspective, as the VZV vaccine is a live vaccine, its administration (2 doses, 1 mo apart) should be carried out at least 4-3 wk before starting immunosuppressive therapy[12,52] or 3-6 mo after stopping it. IBD patients are also at increased risk of developing herpes zoster (HZ). Due to diffuse concurrent use of immunosuppressant agents, clinical manifestations are often more severe, and the risk of complications such as post-herpetic neuralgia, central nervous system and ocular involvement are enhanced [164, 165] . Corticosteroids and thiopurines (especially in combination with anti-TNF medication) are known risk factors linked to HZ infection [32, 33, 166] . Recently tofacitinib has also been observed to be related in a dose-dependent manner to HZ, with additional risk conferred by older age, diabetes mellitus, corticosteroids therapy and prior anti-TNF failure [167, 168] . The diagnosis of HZ is usually based on the clinical presentation (unilateral, usually painful vesicular-papular eruption with a defined dermatomal distribution). However, since immunocompromised subjects may have an atypical presentation (hemorrhagic skin lesions affecting multiple dermatomes), real-time PCR may confirm the diagnosis. Antiviral therapy must be started in IBD patients with HZ, even after 72 h from presentation. Patients with disseminated HZ should be hospitalized for intravenous acyclovir therapy (10 mg/kg every 8 h). On the other hand, oral therapy is usually sufficient for the initial treatment of uncomplicated HZ. Regimen options last 7 days and include valacyclovir (1 g 3 times daily), famciclovir (500 mg 3 times daily) and acyclovir (800 mg 5 times daily). Two types of zoster vaccine are available: the first one is a live attenuated vaccine, which is contraindicated in patients receiving moderate or high-dose immunosuppressive therapy and recently a new recombinant glycoprotein E vaccine has become available. The vaccine is administered twice, at 0 and 2-6 mo. Recombinant vaccine has been proven to be highly effective in reducing HZ risk and postherpetic neuralgia among adult subjects[169]; thus, the ACIP recommends it for use in immunocompetent adults aged ≥ 50 years [170] . There are insufficient data to make recommendations regarding zoster vaccination in immunosuppressed patients, but initial evidence suggests good safety and immunogenic profile in this subgroup of patients [171] [172] [173] . Therefore, it seems to be an acceptable strategy, to propose recombinant vaccine in patients with uncontrolled severe disease activity, history of shingles, a scheduled therapy with tofacitinib, treated with azathioprine and aged > 40 years, and to all patients aged > 50 years [161] .

EBV is a ubiquitous herpesvirus with a seroprevalence >90% worldwide. It is responsible for infectious mononucleosis (IM), and after primary infection persists asymptomatically lifelong in latently-infected circulating B-lymphocytes [174] . EBV infection is associated with different types of malignancies, including B cell lymphomas, T cell lymphomas, Hodgkin lymphoma and nasopharyngeal carcinomas [175] [176] [177] . The incidence rate of lymphoproliferative disorders is much higher in IBD patients than in the general population. The relationship between immunosuppressive drugs (in particular, evidence seems to suggest that thiopurines have specific additional risks [178, 179] ) and EBV infection may be implicated in the pathogenesis of this disease [180, 181] . In addition, severe EBV diseases such as fatal infectious mononucleosis and hemophagocytic lymphohistiocytosis occur when primary infection develops in immunosuppressed patients [182] [183] [184] . Therefore, it seems relevant to determine EBV serology status by testing EBV IgG before starting immunomodulator therapy. In EBV seronegative patients, anti-TNF monotherapy should be preferred over thiopurines [12] . The diagnosis of acute EBV infection is made in the presence of IgM VCA and the absence of IgG EBNA antibodies. When primary infection is recognized, immunomodulator therapy should be reduced or discontinued July 21, 2021 Volume 27 Issue 27 if possible. Advice from a hematologist/oncologist is required when lymphoproliferative disease is suspected.

On March 11th, 2020 the World Health Organization declared coronavirus disease 19 (COVID-19) a global pandemic, marking one of the most intense passages in recent history. The range of symptomatic infection goes from mild to critical; >80% of cases are not severe [185] , but morbidity and mortality are not negligible. Current evidence shows that the IBD population does not have an increased prevalence of SARS-CoV-2 infection [186] [187] [188] and immunomodulators, biologics, or Janus Kinase inhibitors do not represent a risk factor for SARS-CoV-2 infection and more severe COVID-19 [189, 190] .

On the other hand, in several studies of IBD patients with COVID-19, a trend towards an adverse outcome with concomitant corticosteroids was reported [191] . COVID-19 may occur early with gastrointestinal symptoms (anorexia, nausea, vomiting, abdominal pain, and diarrhea) [192] simulating IBD manifestations. For that reason, patients with a suspected IBD flare should be tested to exclude SARS-CoV-2 infection, especially before initiation of biologics [193] . When IBD patients are diagnosed with COVID-19, in its current state, several consensuses and expert opinions propose discontinuation of thiopurines, methotrexate, and JAK inhibitors and extend the interval of administration for biological drugs until nasopharyngeal swab PCR-SARS-CoV-2 tests results are negative or 3 after days of no fever and clinical improvement [194, 195] . Since IBD patients were ruled out of the SARS-CoV-2 vaccine clinical trials, questions regarding the safety and effectiveness in patients with IBD are currently unanswered. As the COVID-19 vaccines available use mRNA-based technology (Pfizer/Biontech, ModeRNA) or non-replicating adenoviral vectors expressing the spike protein (AstraZeneca/Oxford, J&J, Sinovac, Sputnik V) the International Organization for the Study of Inflammatory Bowel Disease (IOIBD) recommends vaccinating all patients with IBD as soon as they are able to receive the vaccine, regardless of immune-modifying therapies [196] . The exception is for any liveattenuated virus vaccines or replication-competent viral vector vaccines that may come to market. Even The British Society of Gastroenterology agrees, strongly supporting SARS-CoV-2 vaccination in patients with IBD, underlining that the critical concerns in patients taking immunosuppressive drugs are more related to the risk of suboptimal immunization rather than the vaccine safety profile [197] .

Due to the alterations in the immune response and the growing adoption of immunomodulators and biologics, IBD patients represent a population exposed to opportunistic infections. The risk of infections is also aggravated by an insufficient immunization status as too frequently observed in patients with IBD. In this field, gastroenterologists should be aware of viral infections that may complicate the IBD course, as they are often challenging to diagnose and treat. Moreover, excess hospitalizations due to viral infections and their related costs, contribute to the human and financial burden of IBD. Prevention is the most important step; a careful workup aimed at avoiding viral infectious disease is essential. Anamnestic and serological screening should be performed in all patients before starting immunosuppressive therapy. In addition, assessing and completing the vaccination status in IBD patients, ideally before immunosuppressive therapy, is the new standard of care. It is also important to provide prophylaxis when indicated to avoid the occurrence of potentially preventable infection. Continued vigilance and a high degree of suspicion is required to monitor for viral infection during maintenance therapy. Even if a direct correlation between a specific immunosuppressant drug and viral infection is not established, special attention must be paid to patients receiving corticosteroids, thiopurines, or combination therapy with thiopurines and anti-TNF agents as they are more prone to contracting opportunistic viral infections, in particular HSV, VZV, CMV, and EBV. It seems prudent to minimize the use of systemic steroids, think of alternatives to steroids and, if used, taper to the lowest possible dose quickly. 

Updated review on immune factors in pathogenesis of Crohn's disease

inflammatory bowel disease, especially steroid-resistant inflammatory bowel disease?

Cytomegalovirus infection in ulcerative colitis: a prospective, comparative study on prevalence and diagnostic strategy

Frequent detection of cytomegalovirus in the intestine of patients with inflammatory bowel disease

Looking into Enteric Virome in Patients with IBD: Defining Guilty or Innocence?

Cytomegalovirus in inflammatory bowel disease: A systematic review

Infection with cytomegalovirus in patients with inflammatory bowel disease: prevalence, clinical significance and outcome

The prevalence and risk factors of cytomegalovirus infection in inflammatory bowel disease in Wuhan, Central China

Cytomegalovirus colitis in hospitalized inflammatory bowel disease patients in Taiwan: a referral center study

Corticosteroids and Thiopurines, But Not Tumor Necrosis Factor Antagonists, are Associated With Cytomegalovirus Reactivation in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

Intestinal cytomegalovirus infection in patients hospitalized for exacerbation of inflammatory bowel disease: a 10-year tertiary referral center experience

Infliximab and the risk of latent viruses reactivation in active Crohn's disease

TNF-alpha is an important pathogenic factor contributing to reactivation of cytomegalovirus in inflamed mucosa of colon in patients with ulcerative colitis: lesson from clinical experience

Infliximab Does Not Worsen Outcomes During Flare-ups Associated with Cytomegalovirus Infection in Patients with Ulcerative Colitis

Novel score predicts risk for cytomegalovirus infection in ulcerative colitis

Cytomegalovirus Reactivation in Ulcerative Colitis Patients

The detection of the cytomegalovirus DNA in the colonic mucosa of patients with ulcerative colitis is associated with increased long-term risk of proctocolectomy: results from an outpatient IBD clinic

CMV Disease in IBD: Comparison of Diagnostic Tests and Correlation with Disease Outcome

Ulcerative Colitis and Cytomegalovirus Infection: From A to Z

British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults

Detection of cytomegalovirus DNA in plasma as an adjunct diagnostic for gastrointestinal tract disease in kidney and liver transplant recipients

Long-term outcome of inflammatory bowel diseases with cytomegalovirus colitis: effect of antiviral treatment

Cytomegalovirus and ulcerative colitis: Place of antiviral therapy

Prior varicella zoster virus exposure in IBD patients treated by anti-TNFs and other immunomodulators: implications for serological testing and vaccination guidelines

BIOBADASER 2. 0 Study Group. Incidence and risk of hospitalisation due to shingles and chickenpox in patients with rheumatic diseases treated with TNF antagonists

Varicella zoster virus infection in inflammatory bowel disease

Varicella zoster virus in inflammatory bowel disease patients: what every gastroenterologist should know

Detection of herpes simplex virus type 1, herpes simplex virus type 2 and varicella-zoster virus in skin lesions. Comparison of real-time PCR, nested PCR and virus isolation

Varicella zoster immune globulin (VARIZIG) administration up to 10 days after varicella exposure in pregnant women, immunocompromised participants, and infants: Varicella outcomes and safety results from a large, open-label, expandedaccess program

Varicella zoster virus vasculopathies: diverse clinical manifestations, laboratory features, pathogenesis, and treatment

The variegate neurological manifestations of varicella zoster virus infection

Increased Risk of Herpes Zoster Infection in Patients With Inflammatory Bowel Diseases in Korea

Herpes Zoster Infection in Patients With Ulcerative Colitis Receiving Tofacitinib

Safety of Tofacitinib for Treatment of Ulcerative Colitis, Based on 4.4 Years of Data From Global Clinical Trials

Efficacy of an adjuvanted herpes zoster subunit vaccine in older adults

Recommendations of the Advisory Committee on Immunization Practices for Use of Herpes Zoster Vaccines

Herpes zoster vaccination in systemic lupus erythematosus: the current status

Oostvogels L; Zoster-028 Study Group. Immunogenicity and safety of the adjuvanted recombinant zoster vaccine in patients with solid tumors, vaccinated before or during chemotherapy: A randomized trial

Zoster-039 study group. Immunogenicity and safety of the adjuvanted recombinant zoster vaccine in adults with haematological malignancies: a phase 3, randomised, clinical trial and post-hoc efficacy analysis

Primary Epstein-Barr virus infection

Relationship between the Epstein-Barr virus and undifferentiated nasopharyngeal carcinoma: correlated nucleic acid hybridization and histopathological examination

Persistence of the Epstein-Barr virus and the origins of associated lymphomas

The Epstein-Barr virus and the pathogenesis of lymphoma

Review article: malignancy on thiopurine treatment with special reference to inflammatory bowel disease

Epstein-Barr virus-positive lymphoma in patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine

Lymphoma and other lymphoproliferative disorders in inflammatory bowel disease: a review

Increased risk of lymphoma among inflammatory bowel disease patients treated with azathioprine and 6-mercaptopurine

Fatal infectious mononucleosis: a severe complication in the treatment of Crohn's disease with azathioprine

Fatal Epstein-Barr virus primo infection in a 25-year-old man treated with azathioprine for Crohn's disease

A nearly fatal primary Epstein-Barr virus infection associated with low NK-cell counts in a patient receiving azathioprine: a case report and review of literature

Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus-Infected Pneumonia in Wuhan, China

2019 novel coronavirus disease (COVID-19) in patients with inflammatory bowel diseases

Systematic Review on Inflammatory Bowel Disease Patients With Coronavirus Disease 2019: It Is Time to Take Stock

Patients with Inflammatory Bowel Disease Are Not at Increased Risk of COVID-19: A Large Multinational Cohort Study

Impact of the COVID-19 outbreak and the serum prevalence of SARS-CoV-2 antibodies in patients with inflammatory bowel disease treated with biologic drugs

Why Do Immunosuppressed Patients with Inflammatory Bowel Disease Not Seem to Be at a Higher Risk of COVID-19?

Italian Group for the Study of Inflammatory Bowel Disease (IG-IBD). Outcomes of COVID-19 in 79 patients with IBD in Italy: an IG-IBD study

Clinical Characteristics of COVID-19 Patients With Digestive Symptoms in Hubei, China: A Descriptive, Cross-Sectional, Multicenter Study

Viral screening before initiation of biologics in patients with inflammatory bowel disease during the COVID-19 outbreak

Expert Opinions on the Current Therapeutic Management of Inflammatory Bowel Disease during the COVID-19 Pandemic

Intractable Diseases, the Health and Labor Sciences Research

Inflammatory Bowel Disease Management During the COVID-19 Outbreak: The Ten Do's and Don'ts from the ECCO-COVID Taskforce

International Organization for the Study of Inflammatory Bowel Disease (IOIBD); International Organization for the Study of Inflammatory Bowel Diseases (IOIBD)

SARS-CoV-2 vaccination for patients with inflammatory bowel disease: a British Society of Gastroenterology Inflammatory Bowel Disease section and IBD Clinical Research Group position statement