SARS-CoV-2, the causative agent of the COVID-19 pandemic, may be transmitted via airborne droplets or contact with surfaces onto which droplets have deposited. In this study, the ability of SARS-CoV-2 to survive in the dark, at two different relative humidity values and within artificial saliva, a clinically relevant matrix, was investigated. SARS-CoV-2 was found to be stable, in the dark, in a dynamic small particle aerosol under the four experimental conditions we tested and viable virus could still be detected after 90 minutes. The decay rate and half-life was determined and decay rates ranged from 0.4 to 2.27 % per minute and the half lives ranged from 30 to 177 minutes for the different conditions. This information can be used for advice and modelling and potential mitigation strategies.

Aims:  Filoviruses are associated with high morbidity and lethality rates in humans, are capable of human‐to‐human transmission, via infected material such as blood, and are believed to have low infectious doses for humans. Filoviruses are able to infect via the respiratory route and are lethal at very low doses in experimental animal models, but there is minimal information on how well the filoviruses survive within aerosol particles. There is also little known about how well filoviruses survive in liquids or on solid surfaces which is important in management of patients or samples that have been exposed to filoviruses. Methods and Results:  Filoviruses were tested for their ability to survive in different liquids and on different solid substrates at different temperatures. The decay rates of filoviruses in a dynamic aerosol were also determined. Conclusions:  Our study has shown that Lake Victoria marburgvirus (MARV) and Zaire ebolavirus (ZEBOV) can survive for long periods in different liquid media and can also be recovered from plastic and glass surfaces at low temperatures for over 3 weeks. The decay rates of ZEBOV and Reston ebolavirus (REBOV) plus MARV within a dynamic aerosol were calculated. ZEBOV and MARV had similar decay rates, whilst REBOV showed significantly better survival within an aerosol. Significance and Impact of the Study:  Data on the survival of two ebolaviruses are presented for the first time. Extended data on the survival of MARV are presented. Data from this study extend the knowledge on the survival of filoviruses under different conditions and provide a basis with which to inform risk assessments and manage exposure to filoviruses.

No abstract

Rapid inactivation of Ebola virus (EBOV) is crucial for high-throughput testing of clinical samples in low-. In response to this outbreak, the international community has deployed an increasing number of Ebola diagnostic laboratories into the main West African countries affected (Guinea, Liberia, and Sierra Leone). Rapid diagnosis of EVD in humans is critical in the management of this disease in outbreak situations, as it allows prompt isolation and the chance to provide the best supportive care to patients, which helps reduce the overall infection rate and break the transmission chain.The preferred clinical sample for testing for Ebola virus (EBOV), an enveloped negative-sense single-strand RNA virus, is EDTA-blood, serum, or plasma with the primary diagnostic technology being real-time PCR (2). Other sample types, such as swabs or urine, may also be received by a laboratory. EBOV is designated in the United Kingdom by the Advisory Committee on Dangerous Pathogens (ACDP) as a hazard group 4 pathogen that must be handled under containment level (CL) 4 standards (biosafety level 4 [BSL4] in other countries). As such stringent laboratory infrastructure and containment procedures are required to handle viable EBOV material, only a few laboratories in Europe and elsewhere are suitably equipped (3). Within the timelines and budgets available, it has been impractical to create this laboratory infrastructure in West Africa, and therefore diagnostic laboratories have relied on methods that rapidly inactivate EBOV prior to routine processing and testing of samples by PCR.Laboratory methods of EBOV inactivation include gamma irradiation (4), nanoemulsion (5), photoinducible alkylating agents (6), and UV radiation (7), but these methods are primarily used for research purposes and may not be practicable in an outbreak situation that is likely to involve a high number of samples but reduced capability for handling and manipulation. In this context, any inactivation method must also be compatible with the EBOV PCR diagnostic approach.The CDC recommends Triton X-100 and heat treatment for 1 h for diagnostic samples containing hemorrhagic fever viruses (8), and this method has been adopted by many laboratories for handling of samples that may contain EBOV (9). Heating (alone or with acetic acid) for 1 h at 60°C has also been shown to reduce the titer of EBOV (10). Other guidelines can be nonspecific, specifying only the need for inactivation but not suggesting how (11) or suggesting generic use of denaturing/lysis buffers and/or heat (12). In the United Kingdom, the Advisory Committee on Dangerous Pathogens guidelines state that samples from confirmed cases may be processed in a containment level 2 laboratory using routine autoanalyzers if a containment level 4 laboratory is not available and provided specific procedures are followed (13). Within these guidelines, which encompass the application of multiple clinical tests, there is no specific requirement to inactivate EBOV (or other viral hemorrhagic fever agents) within a sa...

Normal immunocompetent mice are not susceptible to non-adapted filoviruses. There are therefore two strategies available to establish a murine model of filovirus infection: adaptation of the virus to the host or the use of genetically modified mice that are susceptible to the virus. A number of knockout (KO) strains of mice with defects in either their adaptive or innate immunity are susceptible to non-adapted filoviruses. In this study, A129 α/β -/- interferon receptor-deficient KO mice, strain A129 IFN-α/β -/-, were used to determine the lethality of a range of filoviruses, including Lake Victoria marburgvirus (MARV), Zaire ebolavirus (ZEBOV), Sudan ebolavirus (SEBOV), Reston ebolavirus (REBOV) and Côte d'Ivoire ebolavirus (CIEBOV), administered by using intraperitoneal (IP) or aerosol routes of infection. One hundred percent mortality was observed in all groups of KO mice that were administered with a range of challenge doses of MARV and ZEBOV by either IP or aerosol routes. Mean time to death for both routes was dose-dependent and ranged from 5.4 to 7.4 days in the IP injection challenge, and from 10.2 to 13 days in the aerosol challenge. The lethal dose (50 % tissue culture infective dose, TCID(50)) of ZEBOV for KO mice was <1 TCID(50) ml(-1) when administered by either the IP or aerosol route of infection; for MARV the lethal dose was <1 TCID(50) ml(-1) by the IP route of infection and <10 TCID(50) ml(-1) by the aerosol route. In contrast, there was no mortality after infection with SEBOV or REBOV by either IP or aerosol routes of infection; all the mice lost weight (~15 % loss of group mean body weight with SEBOV and ~7 % with REBOV) but recovered to their original weights by day 14 post-challenge. There was no mortality in mice administered with CIEBOV via the IP route of infection and no clinical signs of infection were observed. The progression of disease was faster following infection with ZEBOV than with MARV but ultimately both viruses caused widespread infection with high titres of the infectious viruses in multiple organs. Histopathological observations were consistent with other animal models and showed widespread organ damage. This study suggests that MARV and ZEBOV are more virulent when administered via the IP route rather than by aerosol infection, although both are highly virulent by either route. The KO mouse may provide a useful model to test potential antiviral therapeutics against wild-type filoviruses.

Knowledge on haemostatic changes in humans infected with Ebola virus is limited due to safety concerns and access to patient samples. Ethical approval was obtained to collect plasma samples from patients in Sierra Leone infected with Ebola virus over time and samples were analysed for clotting time, fibrinogen, and D-dimer levels. Plasma from healthy volunteers was also collected by two methods to determine effect of centrifugation on test results as blood collected in Sierra Leone was not centrifuged. Collecting plasma without centrifugation only affected D-dimer values. Patients with Ebola virus disease had higher PT and APTT and D-dimer values than healthy humans with plasma collected in the same manner. Fibrinogen levels in patients with Ebola virus disease were normal or lower than values measured in healthy people. Clotting times and D-dimer levels were elevated during infection with Ebola virus but return to normal over time in patients that survived and therefore could be considered prognostic. Informative data can be obtained from plasma collected without centrifugation which could improve patient monitoring in hazardous environments.

Deposition of Burkholderia pseudomallei within either the lungs or nasal passages of the Balb/c murine model resulted in different infection kinetics. The infection resulting from the inhalation of B. pseudomallei within a 12 μm particle aerosol was prolonged compared to a 1 μm particle aerosol with a mean time-to-death (MTD) of 174.7 ± 14.9 h and 73.8 ± 11.3 h, respectively. Inhalation of B. pseudomallei within 1 μm or 12 μm particle aerosols resulted in a median lethal dose (MLD) of 4 and 12 cfu, respectively. The 12 μm particle inhalational infection was characterized by a marked involvement of the nasal mucosa and extension of bacterial colonization and inflammatory lesions from the olfactory epithelium through the olfactory nerves (or tracts) to the olfactory bulb (100%), culminating in abscessation of the brain (33%). Initial involvement of the upper respiratory tract lymphoid tissues (nasal-associated lymphoid tissue (NALT) and cervical lymph nodes) was observed in both the 1 and 12 μm particle inhalational infections (80–85%). Necrotising alveolitis and bronchiolitis were evident in both inhalational infections, however, lung pathology was greater after inhalation of the 1 μm particle aerosol with pronounced involvement of the mediastinal lymph node (50%). Terminal disease was characterized by bacteraemia in both inhalational infections with dissemination to the spleen, liver, kidneys, and thymus. Treatment with co-trimoxazole was more effective than treatment with doxycycline irrespective of the size of the particles inhaled. Doxycycline was more effective against the 12 μm particle inhalational infection as evidenced by increased time to death. However, both treatment regimes exhibited significant relapse when therapy was discontinued with massive enlargement and abscessation of the lungs, spleen, and cervical lymph nodes observed.

There are no widely available vaccines or antiviral drugs capable of protecting against infection with Venezuelan equine encephalitis virus (VEEV), although an adenovirus vector expressing VEEV structural proteins protects mice from challenge with VEEV and is potentially a vaccine suitable for human use. This work examines whether alpha interferon (IFN-α) could act as an adjuvant for the adenovirus-based vaccine. IFN-α was either expressed by a plasmid linked to the adenovirus vaccine or encoded by a separate adenovirus vector administered as a mixture with the vaccine. In contrast to previous reports with other vaccines, the presence of IFN-α reduced the antibody response to VEEV. When IFN-α was encoded by adenovirus, the lack of a VEEV-specific response was accompanied by an increase in the immune response to the adenovirus vector. IFN-α also plays a direct role in defence against virus infection, inducing the expression of a large number of antiviral proteins. Adenovirus-delivered IFN-α protected mice from VEEV disease when administered 24 h prior to challenge, but not when administered 6 h post-challenge, suggesting that up to 24 h is required for the development of the IFN-mediated antiviral response.