Resolve to Save Lives

In-Depth Science Review

March 21 – 27, 2020

This science review is a snapshot of the new and emerging scientific evidence related to COVID-19 during the period specified. It is a review of important topics and articles, not a guide for policy or program implementation. The findings captured are subject to change as new information is made available. We welcome comments and feedback at

Rendering of the 2019-nCoV virion. Dan Higgins, MAM/CDC/REUTERS

Loss of smell or taste in COVID-19

Main message: There are increased reports of loss of smell or taste in those infected with COVID-19. More information is needed on the frequency, onset and duration of these symptoms to inform COVID-19 screening.

There have been reports of patients with COVID-19 experiencing a loss of sense of smell (anosmia) and loss or changes in sense of taste (ageusia, dysgeusia). The British Rhinological Society and ENT UK issued a joint statement saying there have been reports of isolated anosmia in COVID-19 patients from multiple countries. They suggest that anosmia could be a trigger for self-isolation and for healthcare personal to use PPE when interacting with patients with this complaint. Importantly, they also note that post-viral (non-COVID) anosmia is one of the leading causes of loss of sense of smell in adults, accounting for up to 40% cases of anosmia. The joint statement and other media articles also reported broadly that a study from South Korea found that 30 percent of approximately 2,000 patients who tested positive for the coronavirus reported experiencing anosmia. The origin of this figure has been called into question and it is likely an overestimate. The American Academy of Otolaryngology advises that anecdotal evidence is rapidly accumulating from around the world that anosmia and dysgeusia are common symptoms associated with COVID-19. They propose that these symptoms be added to the list of screening tools for possible COVID-19 infection. They also created an anosmia reporting tool to gather additional evidence on this symptom and COVID-19.

Hydroxychloroquine for COVID-19 prophylaxis

Main message: There is no new robust evidence that Hydroxycholoroquine should be used for COVID-19 prophylaxis. Studies to evaluate this are underway.

On March 23, the Indian Council for Medical Research (ICMR) released an advisory recommending use of the antimalarial drug hydroxychloroquine as a preventive medicine for those who face a high risk of coronavirus infection. There is no robust evidence to support the use of this medication for prophylaxis. In vivo studies of hydroxychloroquine mentioned in the advisory likely include a small treatment trial in France and a Chinese study of 100 patients. A recent article from India which reviewed the evidence for chloroquine and hydroxychloroquine as of March 20 found that evidence of chloroquine and hydroxychloroquine is limited (based on the experimental data and two small human trials) and there is no conclusive evidence for its use in chemoprophylaxis. The authors recommend additional studies to evaluate its use. In the US, there is one trial currently recruiting patients to look at this issue. This trial will use a modification of standard malaria dosing of hydroxychloroquine to provide post-exposure prophylaxis / preemptive therapy. It is scheduled to be complete in May 2020.


(see supplement for more detailed information)

Main message: Information from serological tests are needed to better understand COVID-19 and inform the global response to the pandemic. Groups around the world are working to increase the availability and ensure accuracy of these tests.

The COVID-19 tests currently available in the US involve testing of upper or lower respiratory specimens to detect the presence of viral RNA, which indicates active infection. Several groups are working on serologic tests using blood serum, which would improve our understanding of COVID-19, including:

  • Information on whether someone has ever been infected, even if they never had symptoms
  • Better picture of the burden of disease, and the proportion of infections that were asymptomatic
  • Determination of the infection fatality ratio (proportion of all infections that are fatal)
  • Identification of whether someone is immune to the disease (and could potentially safely re-enter society)
  • An understand how long immunity lasts
  • Facilitate treatment with convalescent plasma

Serologic tests are being used in other countries including Singapore. CDC is reportedly developing serologic tests, as are many other groups. Researchers at Mt. Sinai in New York Hospital have developed the first test and have started testing patient samples. Evidence from several studies (1, 2, 3, 4) from countries looking at antibody response during SARS-CoV-2 infection indicate an antibody response up to 10 days after symptom onset. There is sparse data on duration on immunity, but both SARS and MERS conveyed immunity that lasted years.



Asymptomatic and Presymptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility — King County, Washington, March 2020 (MMWR, 27 March 2020)

Main message: This article presents concerning information on the potential burden of asymptomatic COVID-19 transmission, with 14% of positive patients never having symptoms. This has implications for the design of COVID-19 testing strategies and other disease control activities to account for asymptomatic transmission, especially as physical distancing recommendations are relaxed.

  • Following identification of a case of COVID-19 in a health care worker, 76 of 82 residents of an SNF were tested for SARS-CoV-2; 23 (30.3%) had positive test results,
    • Of the 23 positive, 10 (43%) had symptoms at time of testing, 13 (57%) had no symptoms
      • 10 of these went on to develop symptoms (presymptomatic) and 3 (23% of initially asymptomatic, 13% of total positive) never had symptoms
    • There were large quantities of viral RNA in asymptomatic, presymptomatic, and symptomatic residents, suggesting the potential for transmission regardless of symptoms.
    • Authors concluded that symptom-based screening in SNFs could fail to identify approximately half of residents with COVID-19. Long-term care facilities should take proactive steps to prevent introduction of SARS-CoV-2 (3). Once a confirmed case is identified in an SNF, all residents should be placed on isolation precautions if possible (3), with considerations for extended use or reuse of personal protective equipment (PPE) as needed.

Epidemiology of Covid-19 in a Long-Term Care Facility in King County, Washington

Main message: Long-term care facilities are vulnerable to respiratory disease outbreaks where they can spread rapidly and widely. These facilities must proactively exclude potentially infected staff and visitors, monitor for active infection in residents and implement infection prevention and control measures effectively.

  • A study on a nursing home outbreak in Washington State. The index case tested positive 9 days after symptom onset and 4 days after hospital admission. By 19 days later 167 COVID-19 infections were epi-linked to the facility including over 85% (101/118) of facility residents, 50 staff and 16 visitors.
  • The case fatality rate was 33% for residents, 6% for visitors, and so far none of the 50 infected HCWs have died.
  • The nursing home outbreak resulted in spread to at least 3 other nursing homes through staff rotation and patient transfer.

Neonatal Early-Onset Infection With SARS-CoV-2 in 33 Neonates Born to Mothers With COVID-19 in Wuhan, China (Jama Pediatrics, 26 March 2020)

Main message: Labor and delivery services should maintain strict infection control measures at the time of birth and closely monitor babies born to women with confirmed or possible coronavirus

  • A cohort study of 33 neonates born to infected mothers in Wuhan, with 3 neonates (9%) testing positive for COVID-19. Symptoms and disease severity were mild in these neonates and no deaths occurred.
  • The babies were tested two days after birth, and might have come into contact with the virus in the hospital. Despite this, the authors could not rule out vertical maternal-fetal transmission in this cohort.

Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska Medical Center (MedRxiv preprint, 23 March 2020)

Main message: SARS-CoV-2 is shed during respiration, toileting, and fomite contact, indicating that infection may occur in both direct and indirect contact.

  • During the initial isolation of 13 individuals confirmed positive with COVID-19 infection, air and surface samples were collected in eleven isolation rooms to examine viral shedding from isolated individuals.
  • Many commonly used items, toilet facilities, and air samples had evidence of viral contamination, indicating that SARS-CoV-2 is shed to the environment as expired particles, during toileting, and through contact with fomites.
  • Disease spread through both direct (droplet and person-to-person) as well as indirect contact (contaminated objects and 20 airborne transmission) are indicated, supporting the use of airborne isolation precautions.


Association of Cardiac Injury with Mortality in Hospitalized Patients With COVID-19 in Wuhan, China. (JAMA Cardiology, 25 March 2020)

Main message: Cardiac injury is a common condition among patients hospitalized with COVID-19, and it is associated with higher risk of in-hospital mortality

  • Cohort study of 416 consecutive patients with confirmed COVID-19 in Wuhan, China
  • Cardiac injury (by biomarker elevation, not ECG or echocardiography) occurred in 20% of patients during hospitalization, and it was an independent risk factor for in-hospital mortality

Cardiovascular Implications of Fatal Outcomes of Patients with Coronavirus Disease 2019 (COVID-2019) (JAMA Cardiology, 27 March 2020)

Main message: SARS-CoV-2 can attack the heart, especially in those with underlying cardiovascular disease, and can result in severe illness or death.

  • Case series study of 187 patients with COVID-19 in Wuhan, China
  • Of the 187 patients, 28% had myocardial injury which resulted in cardiac dysfunction and arrhythmias.
  • Myocardial injury is significantly associated with fatal outcome from COVID-19.
  • The prognosis for patients with underlying cardiovascular disease but without myocardial injury was relatively favorable.

Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia (NEJM, 26 March 2020)

Main message: There is evidence that human-to-human transmission has occurred in Wuhan, China since the beginning of December 2019.

  • Study of the first 425 confirmed cases in Wuhan, Hubei Province, China.
  • The majority of cases in Wuhan prior to January 1, 2020 were linked to the Huanan Seafood Market while only 8.6% of subsequent cases were linked to the market.
  • The mean incubation period was 5.2 days and the basic reproductive number was estimated to be 2.2. The epidemic doubled in size every 7.4 days during the early stages.

Non-pharmaceutical interventions

Evidence of initial success for China exiting COVID-19 social distancing policy after achieving (Imperial College MRC, 24 March 2020)

Main message: There is evidence that after very intense social distancing which resulted in containment, China has successfully exited their stringent social distancing policy, which has implications for other countries in later waves of the pandemic.

  • In response to the fast-growing COVID-19 epidemic, China imposed strict social distancing in Wuhan on 23 January 2020 followed by similar measures in other provinces.
  • For the first time since the outbreak began there have been no new confirmed cases caused by local transmission in China reported for five consecutive days up to 23 March 2020
  • The authors estimated transmissibility from reported cases and compared those estimates with daily data on within-city movement as a proxy for economic activity. Initially, within-city movement and transmission were very strongly correlated in the 5 provinces most affected by the epidemic and Beijing. However, that correlation fell away quickly, especially outside Hubei, and is no longer apparent even though within-city movement has started to increase.
  • A similar analysis for Hong Kong shows that intermediate levels of local activity can be maintained while avoiding a large outbreak.
  • This suggests that after very intense social distancing which resulted in containment, China has successfully exited their stringent social distancing policy to some degree, and that, with the absence of circulating virus, this has not resulted in a second wave of infections at this time.


Will a rise in outdoor temperature affect COVID-19?

Not yet clear. Changes in weather alone (i.e., increase of temperature, humidity or precipitation as spring and summer months arrive in the North Hemisphere) will not necessarily lead to declines in COVID-19 case counts without the implementation of extensive public health interventions (Luo et al.). Generally, coronaviruses do survive for shorter periods of time at higher temperatures and higher humidity than in cooler or dryer environments. However, we don’t have direct data for this virus, nor do we have direct data for a temperature-based cutoff for inactivation at this point. The necessary temperature would also be based on the materials of the surface, the environment, and other factors. (CDC)

Suggested citation: Cash-Goldwasser S, Kardooni S, Cobb L, Bochner A, Bradford E and Shahpar C. In-Depth COVID-19 Science Review March 21 – 27, 2020. Resolve to Save Lives. 2020 April 3. Available from

Science Review