To mitigate a risk, it’s essential to first understand it. For example, if I were planning to hike the John Muir Trail/PCT in the early-season, I’d want to know about hazardous creek crossings. And if I was planning to drink water from natural sources on that trip, I would want to be familiar with the pros and cons of purification techniques.
This fact-based approach towards risk is central to both my personal and guided backpacking trips.
So before I get to specific coronavirus best practices, let’s start by discussing what we know — and, equally important, what we don’t yet know — about Covid-19, with an emphasis on the most relevant facts for an outdoor audience.
Our understanding of Covid-19 is rapidly changing. The information on this page was accurate as of the publishing date. If you feel that it has errors or omissions, please leave a comment.
This page was last updated on May 27, 2020.
This is a four-part series of backcountry best practices in the coronavirus era, and should be read as a whole.
- Executive summary
- Part 1 || Covid-19: Objective risk assessment
- Part 2 || New normals: Policies and codes of conduct
- Part 3 || Navigating restrictions on backcountry use
Covid-19 is a novel strain of coronavirus, and is one of seven known coronavirus strains that are human transmitted. These strains are an extremely common cause of colds and other upper respiratory infections (source).
A person may have Covid-19 if they have (source):
- A cough, and/or
- Shortness of breath;
Or at least two of the symptoms below:
- Repeated shaking with chills
- Muscle pain
- Sore throat
- New loss of taste or smell
Over the course of the disease, most persons with Covid-19 will experience the following (source):
- Fever (83–99%)
- Cough (59–82%)
- Fatigue (44–70%)
- Anorexia (40–84%)
- Shortness of breath (31–40%)
- Sputum production (28–33%)
- Muscle aches, or myalgias (11–35%)
Headache, confusion, rhinorrhea, sore throat, hemoptysis, vomiting, and diarrhea have been reported but are less common (<10%). Some persons with Covid-19 have experienced gastrointestinal symptoms such as diarrhea and nausea prior to developing fever and lower respiratory tract signs and symptoms.
Covid-19 may have additional long-term consequences for some patients (source).
Perhaps 25 percent of those who contract Covid-19 will not show any symptoms. Determining the exact prevalence of asymptomatic carriers is made difficult by the lack of widespread testing and the inaccuracy of current tests (source).
The time from exposure to symptom onset (known as the incubation period) is thought to be three to 14 days, though symptoms typically appear within four or five days after exposure (source).
People with Covid-19 may be contagious for one to three days before they show symptoms. These presymptomatic carriers are a particular challenge to containment strategies (source).
Progression of severe cases
The median time to acute respiratory distress syndrome (ARDS) ranged from 8 to 12 days, and the median time to admission into an intensive care unit (ICU) ranged from 10 to 12 days (source).
Risk of hospitalization due to Covid-19 increases with age. According to CDC Planning Scenarios released in May 2020, “current best estimate” hospitalization rates are:
- 0-49 years-old: 1.7 percent
- 50-64 years-old: 4.5 percent
- 65-74 years-old: 7.4 percent
- Overall: 3.4 percent
These estimates have been revised downwards since March, when hospitalization rates were estimated to be about two times greater (source).
Certain preexisting conditions dramatically increase the risk of hospitalization. Approximately 90 percent of hospitalized Covid-19 patients had an underlying condition, notably (source):
- Hypertension (50 percent)
- Obesity (48 percent)
- Chronic metabolic disease, e.g. diabetes (36 percent)
- Chronic lung disease (35 percent)
- Heart disease (28 percent)
According to the CDC, “current best estimate” for mortality rate in the US is (source):
- 0-49 years-old: 0.05 percent
- 50-64 years-old: 0.02 percent
- 65+ years-old: 1.3 percent
- Overall: 0.4 percent
These estimates are substantially lower than previously believed, which reflects the widespread testing shortage and the unexpectedly high number of asymptomatic cases. Among Covid-19 cases confirmed with testing, the mortality rate ranges from 0.1 percent in Qatar to 15.8 percent in Belgium. In the US, it’s 5.8 percent. This huge variability is a function of testing, country demographics, the quality of care, and data accuracy (source).
Like the hospitalization rate, the mortality rate increases with age. I’ve struggled to find recent national data; as of late-April in New York City, death rates were:
- 20-29 years-old: 0.2 percent
- 30-39 years-old: 0.2 percent
- 40-49 years-old: 0.4 percent
- 50-59 years-old: 1.3 percent
- 60-69 years-old: 3.6 percent
- 70-79 years-old: 8.0 percent
- 80+ years-old: 14.8 percent
I’ve also struggled to find mortality data that looks specifically at underlying conditions. But it seems reasonable that the relationship between underlying conditions and hospitalizations (90 percent) also holds true for the relationship between underlying conditions and mortality.
Relative to other respiratory diseases, Covid-19 is substantially less fatal than severe acute respiratory syndrome (SARS-CoV) or Middle East respiratory syndrome (MERS), which had mortality rates of 10 and 34 percent, but still several times more fatal than the seasonal flu (0.1 percent) (source). For specific mortality rates of the influenza, refer to CDC data.
The infectious dose is the amount of virus needed to establish an infection. Scientists do not yet know how many virus particles of Covid-19 are needed to trigger infection. Based on the global spread of the virus, it’s clearly very contagious. Two potential explanations (source):
- Few particles are needed for infection;
- Infected people release a lot of virus in their environment.
Early data from multiple contact tracing studies (source and source) suggest that close and prolonged contact is required for transmission, and that the risk is highest in enclosed environments with multiple people, including but not limited to:
- Long-term care facilities,
- Homeless shelters,
- Birthday parties, weddings, and funerals,
- Office buildings,
- Business conferences,
- Meat processing plants, and
- Crowded restaurants and bars.
Casual and short interactions are not the main cause of the epidemic.
To minimize your Covid-19 risk, avoid the three C’s: Conversations in poorly ventilated Closed, Crowded spaces.
The virus that causes Covid-19 is thought to spread mainly through respiratory droplets produced when an infected person coughs, sneezes, or spits while talking. These droplets can:
- Land in the mouth, nose, or eye of a person nearby,
- Be inhaled into the lungs, or
- Introduced into the body by touching the nose, mouth, or eyes with an infected surface, like your fingers.
Spread is more likely when people are in close contact with one another, within about 6 feet (source).
Covid-19 particles have been found in finer aerosols, such as from exhaled breath (source), but it’s uncertain if these particles are sufficient to cause infection (source). In an outdoor setting, these aerosols are probably less of a concern than in confined spaces with many people and poor airflow.
Particles of Covid-19 have been shown to stay viable on surfaces like printing paper (3 hours) and plastic (3 to 7 days). But, like aerosols, it’s unclear if the amounts are sufficient to cause infection, and infection is entirely dependent on having a path into the respiratory system (source).
On May 20, the CDC updated its explanation for how Covid-19 spreads. It now says that surface-to-person transmission is “possible” but “is not thought to be the main way the virus spreads.”
Water and food
I have not found information on the transmissibility of Covid-19 in water. For good measure, treat natural sources with chlorine dioxide or a UV light, two recommended water purification techniques that are effective against viruses.
Scant research has been done on the transmission of Covid-19 in an outdoor setting. A study of 318 outbreaks with 1245 confirmed cases in China traced only two cases (0.16 percent) to outdoor transmission. However, the study did not account for the proportion of time spent outdoors by the study group.
Intuitively, it would seem more difficult to absorb an infectious dose while outside, because Covid-19 particles are dispersed by airflow and probably also killed fairly quickly by sunlight (source). This article discusses infectious dose in the context of hiking, running, and cycling outdoors.
Two kinds of tests are available for COVID-19:
- A viral test tells you if you have a current infection.
- An antibody test tells you if you had a previous infection
An antibody test may not be able to show if you have a current infection, because it can take 1-3 weeks after infection to make antibodies. We do not know yet if having antibodies to the virus can protect someone from getting infected with the virus again, or how long that protection might last (source).
It’d be enormously helpful if testing for Covid-19 was more widespread and accurate. But it hasn’t been; it’s not yet; and it probably won’t be in time for the 2020 backpacking season. Read this op-ed for a good synopsis of the situation.
There is no cure for Covid-19. One drug, remdesivir, has been shown to modestly reduce recovery time (source), and was granted emergency FDA authorization on May 1, 2020.
Antibiotics aren’t effective against viral infections such as Covid-19 (source).
The CDC recommends resting and hydrating to help manage symptoms at home.
To reduce the risk of contracting or spreading Covid-19, health experts recommend three measures:
1. Social distancing
The most effective method to reduce Covid-19 risk is avoiding close contact (within 6 feet) with others for a prolonged period of time to prevent the transmission of respiratory droplets.
The exact length of time that constitutes a “prolonged period” is not certain. Recommendations range from just a few minutes in a healthcare setting, to 10 to 30 minutes outside of one (source).
2. Wear a face covering
When social distancing cannot be practiced, wearing a non-medical mask may protect you from others, and others from you. Masks should be washed periodically.
The efficacy of homemade masks is questionable due to cloth porosity and imperfect seals (source). I thought one article described the problem well by likening wearing masks to using chicken wire for window screens, and then also citing a 2015 study that found “a lack of substantial evidence to support claims that facemasks protect either patient or surgeon from infectious contamination.” A more recent study (not yet peer-reviewed) specific to Covid-19 found evidence to support their use.
Until there is more clear science, it seems at least fair to say that a face covering might be a “better than nothing” preventative measure. And the cost and effort of compliance is minimal.
3. Wash your hands
To remove viruses you have picked up from others or from surfaces, wash your hands for at least 20 seconds with soap and warm water. Even standard soap is more effective than alcohol-based hand sanitizer, though sanitizer will also work and it’s sometimes more convenient.
Leave a comment!
- Is this page in error, or not clear?
- What important facts about Covid-19 have been omitted?