Is SARS-CoV-2 transmitted by asymptomatic and pre-symptomatic infected individuals?

Key Findings@#Asymptomatic and pre-symptomatic transmission of SARS-CoV-2 may occur. • Manifestations of COVID-19 are highly varied and may include asymptomatic cases, who do not manifest with any signs and symptoms despite testing positive for COVID-19 by viral nucleic acid tests. Pre-symptomatic cases are infected individuals who are still in their incubation period, hence do not exhibit any symptoms yet but eventually develop symptoms. • As of June 2020, only 586 (2.8%) of the 20,990 active cases in the Philippines were classified as asymptomatic, but it is unclear whether cases are pre-symptomatic or carriers (true asymptomatic). • Based on 36 observational studies (case reports, case series, cross-sectional and cohort studies) and 9 statistical modeling analysis, asymptomatic and pre-symptomatic transmission of SARS-CoV-2 may occur. However, 3 studies reported no transmission from pre-symptomatic and asymptomatic cases. • Studies on viral load comparing symptomatic cases with pre-symptomatic and asymptomatic cases reported contradicting results. The duration of viral shedding was significantly longer for symptomatic patients compared to asymptomatic patients but similar for asymptomatic and pre-symptomatic patients. • Therewas no difference in the transmission rates of symptomatic and asymptomatic cases. However,the estimated infectivity and probability of transmission was higherfor symptomatic cases compared to asymptomatic cases, but results were imprecise due to a wide confidence interval. • The World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) recognize the possibility of pre-symptomatic and asymptomatic transmission. According to WHO, current evidence suggests asymptomatic cases are less likely to transmit the virus than symptomatic cases.

Should Bacillus Calmette–Guérin (BCG) vaccine be used in the prophylaxis of COVID-19?

@#At present, there is insufficient evidence to support the use of BCG vaccine as prophylaxis for COVID-19. Bacillus Calmette Guerin (BCG) vaccine is an attenuated microorganism derived from bovine tubercle bacillus and is being given to prevent severe tuberculosis. BCG vaccination may enhance production of antibodies and pro-inflammatory cytokines such as interleukin (IL)-1β and tumor necrosis factor (TNF). BCG may lead to increased CD4 and CD8 T-cell activity on subsequent viral infection. Ecological studies on the effect of BCG vaccination policy on COVID-19 outcomes have conflicting results and are prone to bias from confounders. There is insufficient evidence on the efficacy and safety of BCG vaccine for COVID-19 prophylaxis. Thirteen clinical trials are ongoing among high-risk groups (healthcare workers, elderly, police officers) to evaluate the efficacy and safety of BCG vaccine in preventing COVID-19 and its severe symptoms. WHO does not recommend the use of BCG vaccine as prophylaxis against COVID-19. Adverse events of BCG vaccine range from mild local cutaneous reactions to systemic adverse events such as abscess, lymphadenopathy and osteomyelitis.

What are the effective methods of decontaminating N95 mask for reuse?

KEY FINDINGS@# Based on laboratory-based studies, ultraviolet germicidal irradiation (UVGI), microwave generated steam, warm moist heat, and hydrogen peroxide vapor (HPV) were able to reduce the load of influenza viruses (A/H5N1, H1N1) or G. stearothermophilus and at the same time maintain the integrity of N95 respirators. • Considering the current pandemic, there is a potential for shortage of N95 facepiece filtering respirator (FFR) for healthcare workers. • No studies in humans were found comparing effectiveness of N95 post-decontamination. • Laboratory based studies done on influenza virus (A/H5N1, H1N1) have shown that ultraviolet germicidal irradiation, microwave generated steam, or warm moist heat was able to reduce the viral load by as much as 4 log and at the same time maintain respirator performance by keeping the percent penetration below 5% and the pressure drop within standards. • While UVGI was able to maintain integrity of FFRs up to 3 cycles, microwave generated steam may melt the metallic components of certain N95 masks. • Hydrogen peroxide vapor (HPV) had minimal effect on respirator performance and structural integrity up to 20 cycles and was also effective in eradicating G. stearothermophilus and aerosolized bacteriophages. • Bleach, ethanol and isopropanol all affected the mean penetration of the mask beyond the 5% limit. • The Centers for Disease Control (CDC) does not recommend decontamination then reuse of FFRs as standard care but decontamination with UVGI, HPV or moist heat may be considered as an option in FFR shortages.