Harvard Professor Issues FAQ on Coronavirus
Dr. Megan Murray is the Ronda Stryker and William Johnston Professor of Global Health at Harvard Medical School and director of research at Partners In Health and at the Brigham and Women’s Hospital Division of Global Health Equity in Boston. She has decades of experience as an epidemiologist and infectious disease specialist and has managed multidisciplinary research teams whose work has spanned continents.
Below, Megan provides valuable insights on how the new coronavirus spreads, whether a vaccine is in the works, and what everyone can do to reduce their risks of infection. Her answers have been condensed and edited from this original version of the FAQs.
How is it transmitted?
COVID-19 is a respiratory virus (like the common cold) and is spread through respiratory droplets, meaning drops of fluid from the nose or mouth that are emitted during coughs, sneezes, or even talking. It is possible that some of the viral particles emitted this way end up on surfaces (door handles, subway poles, coins) where they might remain viable. These objects then become “fomites,” inanimate objects that can transfer infection between people.
It is also possible that COVID-19 can be transmitted as an aerosol—in other words, airborne, through direct inhalation of the virus—but so far, there is no conclusive evidence of that. The virus also has been identified in stool and, less often, in other body fluids such as blood or urine, raising the possibility that other routes of transmission are possible, although it is not clear if that has contributed to the outbreak.
What are the symptoms and clinical course of the disease?
COVID-19 disease usually begins with mild fever, dry cough, sore throat, and malaise. Unlike the coronavirus infections that cause the common cold, it is not usually associated with a runny nose. In the early phase of the disease, illness is usually mild. Most often—in about 80 percent of cases—it remains mild and may not require direct medical intervention.
About 14 percent of people develop severe pneumonia accompanied by hypoxia (lack of oxygen) and 5 percent are considered critical, meaning they experience respiratory failure requiring mechanical ventilation.
Although we know that older people and those with heart problems or diabetes are at especially high risk for severe effects, it is not yet confirmed why these people experience these outcomes.
We’ve heard a lot about the widespread public lockdown in Wuhan, China, travel restrictions, and other measures intended to slow the spread of disease from COVID-19. Can you describe some of those measures, and for example, the differences between quarantine, isolation, and social distancing?
There are several different approaches to restricting movements to control epidemic disease. One approach, isolation, safeguards people with the disease and keeps them away from other people, to try to prevent them from infecting others. But this will only be completely effective if they are diagnosed with the disease at or before the time that they become infectious. If people are infectious before they have symptoms or if some infectious people never develop symptoms at all, transmission can take place before a person is diagnosed and isolated.
For diseases with significant asymptomatic spread, quarantine is used to separate and restrict the movements of people without signs of illness who may have been exposed to an infectious case so that they do not infect others during that period.
A less extreme measure is social distancing—asking people to avoid group settings such as schools, workplaces, or large gatherings. The Wuhan “lockdown” is an example of fairly rigorous social distancing.
All of these methods can have specific downsides. Patients who are isolated within health care facilities may receive suboptimal care if isolation measures make it more difficult for health care workers to attend to them. Quarantine can result in the housing of uninfected people with infectious people who aren’t showing symptoms, and can lead to much higher rates of spread within the quarantine facilities.
If social distancing measures involve loss of employment, education, or routine medical care, they, too, can have serious negative effects on individuals’ physical and mental health, as well as on the economy. In the case of COVID-19, it is unclear whether school closures would be helpful, since few children develop the disease, although we do not yet know if they can be carriers of the infection while not showing symptoms.
Are masks effective in preventing transmission?
First of all, the World Health Organization and Centers for Disease Control are urging the general public not to buy surgical-style or N95 masks, as they are needed by health care workers and patients and are in short supply.
That said, clinicians and patients use several types of masks to prevent infection or slow the spread of the disease. Surgeons use simple masks to prevent themselves from contaminating a surgical site with respiratory droplets, for example. Surgical masks are designed to protect others, but not necessarily the wearer.
Masks known as “N95,” in contrast, are much more heavy-duty and fit tightly around the nose and mouth, blocking most transmission of even small airborne particles. These are worn by patients, or by health care workers who come into close contact with known cases. They are quite uncomfortable and very expensive, but likely reduce transmission of infections through the respiratory route.
Many rumors have been circulating about the disease, including rumors about impacts being seasonal. Will COVID-19 go away with warmer weather?
Some respiratory viruses—such as influenza, RSV, and the coronaviruses that cause the common cold—are seasonal, meaning that they tend to peak during winter months and decline in summer. This seasonal pattern is due to multiple factors. In temperate climates, schools tend to be in session in winter and people tend to congregate in warm buildings in cold weather; these behavioral factors mean that the contact rate is often higher in winter than in summer.
Humidity is known to play a role in the transmission of influenza, as well, with higher rates of transmission during periods when the air is drier—which tends to be the case in winter, in many areas. Some evidence exists that there are seasonal differences in people’s ability to respond to disease with their immune systems.
This is often attributed to vitamin D levels, which are higher in summer because of greater exposure to UV light. This theory is supported by at least one recent analysis, which showed that vitamin D supplementation modestly reduced the occurrence of acute respiratory infections. One study of two other novel coronaviruses—SARS and MERS—found that these persisted on inanimate surfaces for longer periods of time in colder and drier conditions.
In contrast, multiple observers note that COVID-19 has already circulated widely in Singapore, where temperatures are routinely above 80 degrees Fahrenheit. Several studies have compared the epidemic growth rates in different areas in China with differing levels of absolute humidity, and found that changes in weather alone would be unlikely to reduce COVID-19 incidence without the implementation of public health interventions.
Also, of course, seasons are not the same the world over. Even if COVID-19 transmission declines as temperatures rise in the Northern Hemisphere, the virus has already been detected in the Southern Hemisphere, and transmission in those regions could intensify as the weather there cools down.
How long until a vaccine is available for widespread use?
Vaccine development has proceeded at an unprecedented pace. A number of companies and research teams already have candidate vaccines that are either ready or close to ready to trial in humans. However, new vaccines require a complex set of trials to establish safety, immunogenicity, optimal dosing, and more. This process can take more than a year.
There usually are three steps to the clinical trial process needed for vaccines to be commercially available.
Phase 1 trials are usually conducted in small groups of healthy volunteers and are designed to establish whether serious adverse effects occur with escalating doses, and whether the vaccine produces the expected immune response.
Phase 2 trials are designed to replicate Phase 1 results in more diverse populations of volunteers, and to test different vaccine schedules.
Once safety, immunogenicity, and optimal dosing are established, Phase 3 studies are conducted to determine a vaccine’s effectiveness. Phase 3 studies are usually much larger than Phase 1 or 2 studies, and are conducted among people at risk for the infection. During the 2014 Ebola outbreak, however, novel vaccine trial designs were proposed and carried out that allowed reduced sample sizes and a faster trial process.
The completion of all three steps is required for a vaccine to be approved by the Food and Drug Administration. The director of NIAID (National Institute for Allergy and Infectious Disease) has estimated that this process would take 12 to 18 months, and that a commercial vaccine would not be available until after that. The first Phase 1 clinical trial is scheduled to begin in the next two months.
Is it likely that the United States will experience an epidemic?
Most experts believe it is inevitable that COVID-19 will spread in the U.S. It may be possible to slow transmission with some of the isolation methods listed above, but it is unlikely that a vaccine will be available in the near future.
Several factors could make controlling an epidemic especially difficult in the U.S. We are in the midst of a particularly bad influenza season, and it will be difficult to know if one has seasonal flu or COVID-19. This could increase the number of people who need to be tested, making tests more expensive and more logistically challenging. Many patients may be reluctant to get checked for what they consider a mild illness, because those who are uninsured or under-insured may need to pay for testing or for a doctor’s visit. Sick individuals may also be reluctant to stay home from work if they do not have sick leave or paid time off.
What are other consequences of the COVID-19 epidemic?
One of the consequences we’ve seen so far, in Wuhan, is that people who need medical care for other conditions have not been able to obtain that care because hospitals and medical staff are at full capacity dealing with the virus.
News reports describe people in the Wuhan region who have been unable to get dialysis or chemotherapy for the past month. So far, we have been unable to obtain data on whether general mortality has increased in Wuhan as a result of this lack of access to care.
What should I do to reduce my risk of infection?
There are many practical suggestions available from the CDC and WHO on ways to protect oneself from infection, and to prepare for the possibility of an epidemic.
Some of these are obvious:
- Wash your hands frequently.
- Try not to touch your face.
- Avoid people who are coughing or obviously ill.
- Avoid large crowds, if possible.
- Don’t go to work if you are sick. Send your sick workers home.
- If you need to seek medical care for a flu-like illness, call in advance and ask for instructions on where to go.
- If you are sick, don’t go and visit your elderly or immuno-compromised friends and neighbors.
Others are less obvious:
- Consider having a plan for what you might do if social distancing measures are put into effect or if you were quarantined.
- Consider forgoing unnecessary travel (and possibly even necessary travel, if it is to high-risk places).
- Think about how you and your teams can work from home, such as options for conference calls, etc.
- Make sure you have a reasonable supply of any prescription drugs you need.
- Have some emergency provisions on hand, but you don’t necessarily need to go crazy buying up a grocery store’s entire supply of canned goods.
- Consider using a humidifier.