Increased prevalence of gastrointestinal viruses and diminished secretory immunoglobulin a levels in antibody deficiencies.

PURPOSE: Gastrointestinal disease occurs frequently in antibody deficiencies. This study aims to explore the relation between gastrointestinal infections and mucosal homeostasis in patients with antibody deficiencies. METHODS: We performed an observational study including 54 pediatric antibody deficient patients (48 % CVID, 41 % CVID-like, 11 % XLA) and 66 healthy controls. Clinical symptom scores and stool samples were collected prospectively. Stool samples were evaluated for bacteria, parasites, viruses, secretory IgA- and for calprotectin levels. Results were compared between patients and controls. RESULTS: 24 % of antibody deficient patients versus 9 % of healthy controls tested positive for gastrointestinal viruses (p = 0.028). Fecal calprotectin levels were significantly higher in virus positive patients compared to virus negative patients (p = 0.002). However, in controls, fecal calprotectin levels were similar between virus positive and virus negative controls. Moreover, gastrointestinal virus positive patients had low serum IgA levels in 13/14 cases (94 %) versus 40/62 (62 %) patients in the virus negative patient group (p = 0.04). The virus positive patient group also displayed significantly lower secretory IgA levels in stool (median 13 ug/ml) than patients without gastrointestinal viruses detected or healthy controls (median 155 ug/ml) (p = 0.046). CONCLUSION: We here report an increased prevalence of gastrointestinal viruses and gastrointestinal complaints in antibody deficient patients. Patients that tested positive for gastrointestinal viruses showed diminished serum- and secretory IgA levels, and only in patients, virus positivity was associated with signs of mucosal inflammation. These findings suggest that particularly patients with low IgA are at risk for longstanding replication of gastrointestinal viruses, which may eventually result in CVID-related enteropathy.

Most but not all laboratories can detect the recently emerged Neisseria gonorrhoeae porA mutants - results from the QCMD 2013 N. gonorrhoeae external quality assessment programme.

We describe the results of the Quality Control for Molecular Diagnostics 2013 Neisseria gonorrhoeae external quality assessment programme that included an N. gonorrhoeae strain harbouring an N. meningitidis porA gene which causes false-negative results in molecular diagnostic assays targeting the gonococcal porA pseudogene. Enhanced awareness of the international transmission of such gonococcal strains is needed to avoid false-negative results in both in-house and commercial molecular diagnostic assays used in laboratories worldwide, but particularly in Europe.

Performance of different mono- and multiplex nucleic acid amplification tests on a multipathogen external quality assessment panel.

An external quality assessment (EQA) panel consisting of a total of 48 samples in bronchoalveolar lavage (BAL) fluid or transport medium was prepared in collaboration with Quality Control for Molecular Diagnostics (QCMD) (www.qcmd.org). The panel was used to assess the proficiency of the three laboratories that would be responsible for examining the 6,000 samples to be collected in the GRACE Network of Excellence (www.grace-lrti.org). The main objective was to decide on the best-performing testing approach for the detection of influenza viruses A and B, parainfluenza virus types 1 to 3, respiratory syncytial virus (RSV), human metapneumovirus, coronavirus, rhinovirus, adenovirus, Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila by nucleic acid amplification techniques (NAATs). Two approaches were chosen: (i) laboratories testing samples using their in-house procedures for extraction and amplification and (ii) laboratories using their in-house amplification procedures on centrally extracted samples. Furthermore, three commercially available multiplex NAAT tests-the ResPlex (Qiagen GmbH, Hilden, Germany), RespiFinder plus (PathoFinder, Maastricht, The Netherlands), and RespiFinder Smart 21 (PathoFinder) tests-were evaluated by examination of the same EQA panel by the manufacturer. No large differences among the 3 laboratories were noticed when the performances of the assays developed in-house in combination with the in-house extraction procedures were compared. Also, the extraction procedure (central versus local) had little effect on performance. However, large differences in amplification efficacy were found between the commercially available tests; acceptable results were obtained by using the PathoFinder assays.

Lower respiratory tract infection in the community: associations between viral aetiology and illness course.

OBJECTIVES: This study determined associations between respiratory viruses and subsequent illness course in primary care adult patients presenting with acute cough and/or suspected lower respiratory tract infection. METHODS: A prospective European primary care study recruited adults with symptoms of lower respiratory tract infection between November 2007 and April 2010. Real-time in-house polymerase chain reaction (PCR) was performed to test for six common respiratory viruses. In this secondary analysis, symptom severity (scored 1 = no problem, 2 = mild, 3 = moderate, 4 = severe) and symptom duration were compared between groups with different viral aetiologies using regression and Cox proportional hazard models, respectively. Additionally, associations between baseline viral load (cycle threshold (Ct) value) and illness course were assessed. RESULTS: The PCR tested positive for a common respiratory virus in 1354 of the 2957 (45.8%) included patients. The overall mean symptom score at presentation was 2.09 (95% confidence interval (CI) 2.07-2.11) and the median duration until resolution of moderately bad or severe symptoms was 8.70 days (interquartile range 4.50-11.00). Patients with influenza virus, human metapneumovirus (hMPV), respiratory syncytial virus (RSV), coronavirus (CoV) or rhinovirus had a significantly higher symptom score than patients with no virus isolated (0.07-0.25 points or 2.3-8.3% higher symptom score). Time to symptom resolution was longer in RSV infections (adjusted hazard ratio (AHR) 0.80, 95% CI 0.65-0.96) and hMPV infections (AHR 0.77, 95% CI 0.62-0.94) than in infections with no virus isolated. Overall, baseline viral load was associated with symptom severity (difference 0.11, 95% CI 0.06-0.16 per 10 cycles decrease in Ct value), but not with symptom duration. CONCLUSIONS: In healthy, working adults from the general community presenting at the general practitioner with acute cough and/or suspected lower respiratory tract infection other than influenza impose an illness burden comparable to influenza. Hence, the public health focus for viral respiratory tract infections should be broadened.

Multicenter external quality assessment of molecular methods for detection of human herpesvirus 6.

The purpose of this study was to evaluate the performance of laboratories for the detection and quantification of human herpesvirus 6 (HHV-6) by an external quality assessment (EQA) evaluation. The HHV-6 EQA panel consisted of eight samples containing various concentrations of HHV-6 type A (strain GS) or type B (strain Z29), two samples containing other herpesviruses (i.e., human cytomegalovirus [HCMV] and Epstein-Barr virus [EBV]), and two HHV-6-negative samples. Panel samples were prepared in human plasma, heat inactivated, and lyophilized. Panel distribution, data management, and analysis were coordinated by Quality Control for Molecular Diagnostics (QCMD), Glasgow, United Kingdom. Fifty-one laboratories participated and submitted 57 data sets. Eleven (19.3%) data sets were generated using conventional in-house assays, 11 (19.3%) data sets using commercial real-time PCR assays, and 35 (61.4%) data sets using in-house real-time PCR assays. The presence of HHV-6 DNA at viral loads exceeding 6,000 copies/ml was detected by all participants, and over 80% of the participants still reported correct qualitative results for the sample containing just over 200 copies/ml. The false-positivity rate was 1.8% for both the negative samples and the samples containing HCMV or EBV DNA. The majority (23/33; 69.7%) of quantitative data sets were generated using in-house real-time PCR assays. The standard deviations of the geometric means of the samples ranged from 0.5 to 0.7 log(10). The results of this first international EQA demonstrate encouraging analytical sensitivity for the detection of HHV-6-DNA in human plasma, although we observed extensive interlaboratory variation of quantitative HHV-6 DNA results. Standardization needs to be improved to allow further elucidation of the clinical significance of HHV-6 loads.

Persistent and transient hepatitis B virus (HBV) infections in children born to HBV-infected mothers despite active and passive vaccination.

Combined passive and active immunization for newborns very effectively prevents perinatal hepatitis B virus (HBV) infections. In the Netherlands, babies born to hepatitis B surface antigen (HBsAg)-positive women receive passive immunization with hepatitis B and at least three active HBsAg vaccinations. Serological testing for the presence of HBV markers was offered for all infants born to HBsAg-positive mothers between January 2003 and July 2007, after completion of their vaccination schedule. About 75% of the infants (n = 1743) completed their HB-vaccination schedule and participated in the serologic evaluation. Twelve of them (0.7%) were found to be HBV infected. Furthermore, we identified three older children with high levels of anti-HBc, anti-HBs and anti-HBe, while they were HBsAg and HBV DNA negative. This serologic profile is evidence for a resolved HBV infection. In the group of older children (1.5-5 years of age, n = 728), about half of the HBV-infected children (3 of 7) had already cleared their infection at the time of sampling. For a proper evaluation of the efficacy of a new intervention programme to prevent vertical HBV transmission, it is also important to analyse the HBV markers in serum collected when the children are older than 1.5 years. In a programmatic setting, all children born to HBV-infected mothers should be tested not only for the level of anti-HBs but also for the absence of HBsAg, because 2 of the 12 HBV-infected children (17%) had a high level of anti-HBs.

[COVID-19 in nursing homes A study of diagnosis, symptomatology and disease course]. / Covid-19 in verpleeghuizen.

OBJECTIVE: To describe the diagnosis, symptomatology and disease course of COVID-19 in nursing home (NH) residents in the Netherlands. DESIGN: Prospective cohort study. METHOD: Data on NH residents with suspected COVID-19 were collected from the electronic patient records. Data were collected on diagnostic status (COVID-19: confirmed/excluded (using the RT-PCR test)), symptomatology (typical/atypical and other symptoms, body temperature and oxygen saturation) and, in the case of confirmed COVID-19, on disease course (recovered/clinically improved/deteriorated, deceased). We described and compared the symptomatology in NH residents with confirmed COVID-19 and NH residents in whom COVID-19 had been excluded. We also analysed mortality risk using survival analysis. We used registrations from the period 18 March to15 April 2020 for this study. RESULTS: We reported on 1,969 NH residents with suspected COVID-19. The diagnosis was confirmed in 857 patients (43.5%); diagnosis was excluded in 1,112 (56.5%) patients. Among patients with confirmed COVID-19, 65% had coughs, 70% had fever, 33% had shortness of breath, 28% had delirium/confusion and 10% had a sore throat; in patients in whom COVID-19 was excluded these symptoms were experienced in 70%, 47%, 45%, 26% and 13% of patients, respectively. Of the patients with confirmed COVID-19, 48% died within 30 days (95% CI: 36-44%), versus 20% of the patients in whom COVID-19 was excluded (95% CI: 11-15%). CONCLUSION: There is a lot of overlap in symptomatology between NH residents with COVID-19 and those with other acute diseases. An RT-PCR test is required to be able to make the distinction better. The mortality risk in patients with confirmed COVID-19 is significantly higher than in patients in whom covid-19 is excluded.

HIV-1 drug resistance genotyping quality assessment: results of the ENVA7 Genotyping Proficiency Programme.

BACKGROUND: Drug-resistance testing plays a critical role in selection of optimal treatment regimens for HIV infected individuals. Laboratories performing testing must implement quality control measures including external quality assessment. OBJECTIVES: The ENVA7 Programme (2007) was organised by QCMD to assess the performance of laboratories testing for drug-resistance mutations in the HIV-1 Protease and Reverse Transcriptase genes. STUDY DESIGN: The ENVA7 panel consisted of 5 lyophilised plasma samples (HIV-1 subtypes B, C and F). The viruses harboured wild type or resistant genotypes at various positions of the PR and RT genes. All IAS-defined resistance-associated codons were scored in comparison to the consensus sequence for each sample using a scoring system developed to allow simple and standardised comparisons between laboratories and/or technologies. RESULTS: 111 laboratories from 44 countries participated of which 95 submitted 98 datasets. 36 datasets were generated using ViroSeq (Abbott), 27 using TruGene (Siemens) and 35 using in-house assays. CONCLUSIONS: All technologies successfully genotyped each of the panel samples, irrespective of the virus subtype. While the assays for genotypic HIV drug-resistance determination have evolved into reliable and technically capable procedures of generating high quality results, variation in the quality of results is still observed between laboratories.

Molecular detection and typing of influenza viruses: are we ready for an influenza pandemic?

BACKGROUND: We cannot predict when an influenza pandemic will occur or which variant of the virus will cause it. Little information is currently available on the ability of laboratories to detect and subtype influenza viruses including the avian influenza viruses. OBJECTIVES: To assess the ability of laboratories to detect and subtype influenza viruses. STUDY DESIGN: In 2006 QCMD distributed an External Quality Assessment panel for the molecular detection and haemagglutinin subtyping of influenza viruses to 87 laboratories in 34 countries Worldwide, which were given 6 weeks to return results. These data were analysed to assess laboratory performance. RESULTS: Influenza virus positive panel samples were correctly identified by 35-98% of laboratories. The correct haemagglutinin subtype was reported by 32-87% of laboratories that detected the virus: incorrect subtyping results included the reporting of avian influenza viruses as human strains and vice versa. Twelve laboratories reported false positives with some avian influenza viruses reported. CONCLUSIONS: These data suggest that improvements are needed in the molecular detection of influenza viruses and influenza virus A haemagglutinin subtyping. Only rapid and accurate identification of circulating pandemic influenza virus will ensure that the maximum time is available for intervention.

Symptoms of influenza virus infection in hospitalized patients.

BACKGROUND: During influenza outbreaks, fever and cough are the most accurate symptoms in predicting influenza virus infection in the community. OBJECTIVE: To determine the usefulness of fever, cough, and other symptoms for diagnosing influenza virus infection in hospitalized patients. DESIGN: Prospective cohort study. SETTING: Three wards (pulmonology, internal medicine and infectious diseases, and geriatrics) of a tertiary care hospital in the Netherlands. PATIENTS: All patients staying in the wards during peak national influenza activity in the 2005-2006 and 2006-2007 influenza seasons. METHODS: During peak influenza activity, the presence of fever, cough, and/or other symptoms possibly associated with influenza was monitored for all patients, and nose and throat swab samples were taken twice weekly for virologic analysis. RESULTS: Of 264 patients, 23 (9%) tested positive for influenza virus. The positive predictive value of fever and cough for the diagnosis of influenza virus infection was 23% (95% confidence interval, 0%-62%), and the sensitivity was 35% (95% confidence interval, 11%-58%). The combination of symptoms with the highest positive predictive value (40%) was that of cough, chills, and obstructed nose or coryza. The combination of cough and chills or fever had the highest sensitivity (60%). None of the combinations of symptoms had both a positive predictive value and a sensitivity higher than 40%. CONCLUSIONS: Both the sensitivity and the positive predictive value of fever, cough, and/or other symptoms for the diagnosis of influenza virus infection in hospitalized patients are low. The use of these common symptoms for treatment decisions and infection control management will probably be insufficient to contain a nosocomial outbreak, because many influenza cases will remain unidentified.

[Relationship between rubella virus and Fuchs heterochromic uveitis; 2 patients]. / Samenhang tussen rubellavirus en fuchs-heterochromie-uveïtis; 2 patiënten.

Two otherwise healthy men, aged 26 and 29 years, were diagnosed with Fuchs heterochromic uveitis (FHU) on the basis of the presence of iris heterochromia or iris atrophy, stellate corneal precipitates, and/or cataract. Microbiological investigation of aqueous humour demonstrated intraocular antibody production against rubella virus, but not against Toxoplasma gondii, herpes simplex virus or varicella zoster virus. Microbial nucleic acid detection was negative for all pathogens. Some time later, both patients underwent cataract surgery, which improved their vision considerably. FHU is a chronic, generally unilateral iridocyclitis, accompanied by the above-mentioned ophthalmologic manifestations in the absence of systemic disease. Little is known about the pathogenesis ofFHU, but recent publications have provided evidence for the possible involvement of the rubella virus.

Effect of cytomegalovirus infection on T-lymphocytes after lymphocyte-depleted bone marrow transplantation.

The effect of cytomegalovirus (CMV) infection on the repopulation of the peripheral blood with T-lymphocytes was studied in recipients of lymphocyte-depleted bone marrow transplants (BMT) who had hematologic and cytogenetic evidence of engraftment. Lymphocyte depletion was performed using counterflow centrifugation and resulted in a median depletion of 98.4% (range 94.4%-99.8%) of the T cells. Between 8 and 105 days after BMT, the T-cell repopulation was characterized by a relative preponderance of T cells lacking the CD3 marker and a slow repopulation of CD3+, CD4+, and CD8+ T cells. The CD8+ T cells repopulated at a faster rate in patients with CMV infection than in those not infected with CMV. At the end of the 9- to 12-month follow-up period, patients with CMV infection had normal numbers of CD4+ and CD8+ T cells but increased numbers of HNK1+ T cells. Those without CMV infection had subnormal numbers of CD4+ T cells, normal numbers of CD8+ T cells, and numbers of HNK1+ T cells that attained the upper limit of the normal range. Most of the HNK1+ T cells in both patient groups coexpressed the CD8 marker. We conclude that the occurrence of CMV infection in recipients of lymphocyte-depleted BMT is associated with an increase in the number of T cells coexpressing CD8 and HNK1, just as in recipients of nondepleted BMT.

Prevalence of HIV-1 antibody among groups of patients and healthy subjects from a rural and urban population in the Mwanza region, Tanzania.

In April 1987, antibody to HIV-1 was determined in sera from 764 subjects from the Mwanza region in the north of Tanzania. Patients with a clinical suspicion of AIDS were HIV-1 antibody-positive in 65.4% (34 out of 52) and patients admitted for pulmonary tuberculosis in 25% (9 out of 36). In patients attending general outpatient departments (OPD), HIV antibody was found in 12.5% of 48 patients with a history of sexually transmitted disease (STD) and in 10.6% of 141 patients without such a history. In healthy subjects, HIV-1 antibody was present in 6% of 332 pregnant women and in 4.5% of 155 blood donors. Of the blood donors, pregnant women and OPD patients without a history of STD (628 subjects in all), 465 belonged to the rural population of the region and the majority were peasants. In this subgroup, the HIV-1 antibody prevalence was 4.8% in blood donors, 4.9% in pregnant women and 10.3% in OPD patients. This indicates a spread of HIV-1 among the population in this part of Tanzania. Further studies are needed to determine what proportion of the population is affected.

Detection of HIV antibodies in saliva as a tool for epidemiological studies.

OBJECTIVE: To evaluate the use of saliva specimens for the detection of HIV antibodies among high-risk groups in epidemiological studies. DESIGN: Testing of saliva specimens collected by different methods from individuals with known HIV status. The most reliable method was examined for its usefulness in a field study among a high-risk group. METHODS: Saliva samples were obtained either by using a cotton-wool roll ('Salivette') or as 'whole saliva'. HIV antibodies were determined using commercial enzyme-linked immunosorbent assays (ELISA). Confirmation was performed using a line immunoassay or an immunoblot assay. RESULTS: In 'Salivette' samples, HIV antibodies were detected by ELISA in seven out of 22 seropositive individuals. In contrast, testing of 'whole saliva' samples from 79 HIV-seropositive and 115 HIV-seronegative individuals resulted in a 100% correlation with HIV serum status. The positive reaction of 20 'whole saliva' specimens was confirmed in a line immunoassay, whereas in an immunoblot assay only seven specimens were positive, one negative, and 12 indeterminate. In an HIV prevalence study among drug users, 395 'whole saliva' samples were tested in two different ELISA. Both assays showed complete agreement in detecting 58 positive and 337 negative samples. All positive samples were confirmed by the line immunoassay. CONCLUSION: Our study demonstrates that 'whole saliva' specimens are a good alternative to blood samples in epidemiological studies of HIV prevalence in high-risk groups.

Diagnosis of enterovirus infection in the first 2 months of life by real-time polymerase chain reaction.

During summer and fall, enterovirus infections are responsible for a considerable proportion of hospitalizations of young infants. We prospectively studied the incidence of enterovirus infections via real-time polymerase chain reaction (PCR) in blood, feces, and cerebrospinal fluid samples from infants

Sequence analysis of EBV DNA isolated from mouth washings and PBMCs of healthy individuals and blood of EBV-LPD patients.

BACKGROUND: Lymphoproliferative disorder (LPD) caused by Epstein-Barr virus (EBV) is a severe complication of bone marrow transplantation. The EBV strain causing LPD is of either donor or recipient origin, however, available data are limited to only a small number of cases. To obtain solid evidence, comparison of the EBV strain that caused the EBV-LPD with pre-stem cell transplantation (SCT) EBV strains of donor and recipient is imperative. Available techniques rely on the production of EBV transformed lymphoblastoid cell lines and lack sensitivity. OBJECTIVE: The aim of this study was to develop a simple method for EBV sequence analysis on mouth washings (MWs) and peripheral blood mononuclear cells (PBMCs). STUDY DESIGN: EBV DNA was extracted from MWs and PBMCs that were collected from 20 healthy individuals. DNA was used for sequence analysis, using a polymerase chain reaction for the C-terminus of the LMP-1 gene. RESULTS: In seropositive individuals EBV DNA could be detected in 11/14 (79%) MWs and in 13/14 (93%) PBMC samples. Sequence analysis showed that in 11 out of 14 (79%) healthy individuals sequence patterns could be established. In these 11 healthy individuals 13 sequence patterns could be detected. Eleven of these 13 patterns (84.6%) were unique. These results encouraged us to explore the feasibility of this method on EBV DNA isolated from plasma from 9 EBV-LPD patients at time of EBV reactivation. In 7 EBV-LPD patients 8 sequence patterns were detected. Six out of 8 sequence patterns (75%) were unique. CONCLUSION: Our method is suitable for strain identification and we intend to use this technique to evaluate EBV origin in EBV-LPD patients.

Infectious gastro-enteritis: an uncommon cause of diarrhoea in adult allogeneic and autologous stem cell transplant recipients.

The incidence and aetiology of acute diarrhoea in 60 adult allogeneic or autologous stem cell transplant (SCT) recipients was determined in a prospective study. Stool specimens were obtained prior to SCT and on days +20, +40, +60 and +100 post transplant. Microbiological evaluation was performed for pathogenic bacteria, fungi, parasites and viruses. Forty-seven patients were evaluable of whom 31 had a total of 48 acute diarrhoeal episodes. Diarrhoea occurred in 79% of allogeneic and 47% of autologous SCT recipients (P < 0.05). Intestinal infections were found in three of 48 (6%) diarrhoeal episodes. Clostridium difficile with positive toxin was cultured twice and one stool specimen was positive for cryptosporidium. Intestinal pathogens were identified in 13 out of 172 stool specimens from asymptomatic patients and included: rotavirus (4), adenovirus (3), C. difficile, toxin positive (2), and others (4). Graft-versus-host disease was confirmed by biopsy in two of 36 episodes of diarrhoea in allogeneic patients, and in three patients a relationship between reactivation of cytomegalovirus and diarrhoea was suspected. In 40 of 48 (83%) episodes of diarrhoea no clear aetiology could be found.

Enzyme-linked immunosorbent assay for quantitation of toxoplasma antibodies in human sera.

An enzyme-linked immunosorbent assay(ELISA) was developed for the detection of toxoplasma antibodies using a single serum dilution (1:800) in conjunction with a standard curve Antigen was prepared from Toxoplasma gondii cultivated in human cell cultures. A nearly linear relationship was found between the logarithms of the absorbance values of 120 human sera at a dilution of 1/800 and the titres as determined by an end point dilution ELISA. The reproducibility of the single dilution ELISA was excellent; the coefficients of variation for within-day and day-to-day tests were less than 15%. A close correlation was found between the results obtained with ELISA, indirect immunofluorescence (IF), and complement fixation (CF). The titres in ELISA were 20 to 40 times higher than in IF and 200 to 1000 times higher than in CF.

Enzyme-linked immunosorbent assay for measurement of antibody against cytomegalovirus and rubella virus in a single serum dilution.

Enzyme-linked immunosorbent assays (ELISA) were developed for quantifying cytomegalovirus (CMV) and rubella antibodies using a single serum dilution (1/800) in conjunction with a standard curve. A near linear relation was found between the logarithms of absorbance values of sera at a dilution of 1/800 and the titres as determined by an end point dilution ELISA. The reproducibility of the single dilution ELISA was good; the within-test coefficients of variation averaged 7.5% for CMV antibody and 12.4% for rubella antibody. A close correlation was found between ELISA and complement-fixing (CF) antibody titres to CMV and between ELISA and haemagglutination-inhibition (HI) antibody titres to rubella virus. The titres in ELISA were 200 to 1000 times higher than in CF for CMV and 50 to 100 times higher than in HI for rubella virus.

Virus transmission by subcutaneous jet injection.

An animal model was used to establish the risk of transmitting a virus infection by subcutaneous jet injection. Virus transmission was studied with mice chronically infected with LDH virus. The virus infection was transmitted by subcutaneous jet injection in 16 cases out of 49. Other routes of cross-infection were ruled out. Before using the jet injector as a harmless instrument for mass subcutaneous injection, further experiments on the risks of virus transmission should be performed.