Coronavirus disease 2019 (COVID-19)

Incubation period and presymptomatic transmission:

The symptoms of COVID-19 may appear anywhere from 2 to 14 days after exposure to the virus. This timeframe between exposure and symptoms is called the incubation period. During this period, individuals can spread the virus to others even before experiencing symptoms, known as presymptomatic transmission.

Common symptoms:

• Fever
• Cough
• Fatigue

Early symptoms:

• Loss of taste or smell
• Additional symptoms:
• Shortness of breath or difficulty breathing
• Muscle aches
• Chills
• Sore throat
• Runny nose
• Headache
• Chest pain
• Pink eye (conjunctivitis)
• Nausea
• Vomiting
• Diarrhea
• Rash

The severity of symptoms can vary from person to person. Underlying medical conditions may also impact clinical presentation and disease progression. Close monitoring is important if exposed to the virus.

The list of potential COVID-19 symptoms is incomplete. Children generally present with milder versions of the same symptoms seen in adults. Fever, cough, fatigue, and gastrointestinal issues are commonly reported in pediatric COVID-19 cases.

The severity of symptomatic COVID-19 infections ranges widely from mild to severe. Some patients may only experience minor symptoms, while others develop more significant clinical manifestations. Additionally, asymptomatic infections occur when an individual is infected but never develops noticeable symptoms. However, asymptomatic individuals can still pass the virus to others.

For some patients, symptoms may worsen over time. Approximately one week after initial improvement, some patients report exacerbated shortness of breath and develop pneumonia. In long COVID cases, symptoms persist longer than the standard 2-4 weeks duration. Patients experience prolonged fatigue, brain fog, muscle pain and other issues for months.

A severe but rare post-infectious inflammatory condition called multisystem inflammatory syndrome can manifest several weeks after acute COVID-19 illness, particularly in children. The syndrome causes inflammation in multiple organ systems such as the heart, lungs, kidneys, brain, skin, eyes or gastrointestinal organs. Adults may also be affected on rare occasions.

Given the highly variable nature of COVID-19 presentations, close monitoring of symptoms is essential. Asymptomatic individuals should especially adhere to prevention measures to curb further transmission.

If you have COVID-19 symptoms or have been exposed to someone with a confirmed infection, it is critical to contact your healthcare provider right away for guidance.

Your doctor will likely recommend getting tested for COVID-19. Testing is important for receiving appropriate care and limiting potential spread.

In emergencies requiring immediate medical attention, look out for severe symptoms such as:

• Trouble breathing
• Persistent pain or pressure in the chest
• New confusion or inability to arouse
• Bluish lips or face

This list of severe symptoms needs to be more comprehensive. Be sure to inform your healthcare team about any other signs or your entire medical history, as certain groups are at higher risk of serious illness from COVID-19. Individuals who are older or have pre-existing conditions affecting the heart, lungs, kidneys or immune system may experience worse outcomes.

Prompt evaluation is important to manage severe cases and prevent complications properly. Do not delay seeking emergency care if concerning symptoms arise.

Infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the disease known as coronavirus disease 2019 (COVID-19). Current evidence shows that SARS-CoV-2 spreads primarily through respiratory droplets and aerosols exhaled during exhalation, speech, coughs or sneezes by infected individuals.

When in close contact with others, these droplets and aerosols can be directly inhaled or deposited in nearby individuals’ eyes, nose or mouth. The virus has also been shown to spread through airborne transmission over longer distances or durations when very fine droplets remain suspended in the air.

Touching contaminated surfaces and touching the eyes, nose, or mouth represents another potential route of exposure. However, the risk is considered relatively low compared to airborne transmission between individuals in close proximity.

A concerning aspect of COVID-19 is that asymptomatic and presymptomatic infected individuals can unwittingly transmit the virus to others. Furthermore, reinfection, while rare, is … … possible with SARS-CoV-2 as immunity may wane over time. These factors have contributed to the highly contagious nature and ongoing challenges of controlling the spread of this virus.

Risk factors for contracting COVID-19 include

• Close contact with an infected individual: Coming within 6 feet of someone who is confirmed to have COVID-19, especially if they are coughing or sneezing, puts one at risk of exposure to respiratory droplets. Close contact includes sharing meals, living with, or caring for an infected person.
• Exposure to coughs or sneezes: Directly inhaling droplets expelled during coughing or sneezing poses a high transmission risk if the infected person is not wearing a well-fitted mask. Even brief exposures can potentially transmit the virus if it is deposited in the exposed individual’s eyes, nose or mouth.
• Indoor settings with limited ventilation: In enclosed indoor spaces like homes, offices or classrooms with poor air circulation, infectious droplets can remain suspended in the air for longer durations. The risk increases with longer exposure periods spent in these inadequately ventilated areas, especially if masks are not used consistently.

Patients with dementia or Alzheimer’s disease are at a higher risk of severe COVID-19 outcomes, as are those with existing neurological conditions such as a previous stroke. A smoking history can also increase one’s susceptibility to serious illness if infected. Additionally, being overweight or obese has been correlated with a worse prognosis.

The body naturally becomes more vulnerable to respiratory infections as the brain and nervous system age or are damaged by disease. Conditions that impact lung and heart health, like long-term smoking or carrying extra weight long-term, can further compromise how the body deals with any new infection. While many may experience only mild or no symptoms with COVID-19, it is prudent for those in higher-risk groups to take extra precautions to protect their health.

Several medical conditions can increase one’s risk of experiencing severe complications from a COVID-19 infection. These include:

• Cancer: Those undergoing cancer treatment like chemotherapy may have a weakened immune system, putting them more at risk.
• Diabetes: Both type 1 and type 2 diabetes can impact how the body fights viruses and infections. Keeping blood sugar well-controlled is important for health.
• Transplant or HIV/AIDS: Anyone who has received a solid organ transplant (heart, lung, kidney, liver, pancreas, intestine) or a bone marrow transplant and is taking drugs to prevent organ/tissue rejection or suppress the immune system faces higher risks, as does someone with untreated HIV/AIDS.
• Pregnancy: The physical changes and stresses that occur during pregnancy can impact immunity. Pregnant people seem to have an increased risk of severe illness when infected with viruses from the same family as COVID-19.
• Down syndrome: Those with Down syndrome have an extra chromosome, which can impact development, and some have conditions like heart or respiratory issues that increase their COVID-19 risk.
• Substance use disorders: Long-term health issues caused by substance abuse, like lung or heart damage, can increase the chances of complications.

This list covers many but not all medical conditions that may heighten one’s vulnerability. As with any disease, a person’s age, overall health status and underlying state of their immune system play a significant role in how their body responds to an infection like COVID-19.

The Centers for Disease Control and Prevention (CDC) strongly advises that all individuals six months of age and older receive vaccination against COVID-19. Extensive clinical evidence demonstrates that COVID-19 vaccines substantially reduce the risk of adverse health outcomes from SARS-CoV-2 infection, including hospitalisation and mortality. Data also indicates the vaccines may lower an individual’s potential for asymptomatic viral transmission to others in the community.

Concurrent circulation of influenza viruses during the fall and winter months means that respiratory symptoms from COVID-19 or influenza could overlap. Without diagnostic testing, it may be difficult to distinguish between these respiratory infections based on symptoms alone. Therefore, maintaining up-to-date vaccination against both COVID-19 and influenza is prudent. This dual immunisation approach offers multi-factorial protection against serious illness from SARS-CoV-2 or influenza virus exposure.

The U.S. Food and Drug Administration (FDA) has approved or authorised several COVID-19 vaccines:

Moderna and Pfizer-BioNTech COVID-19 vaccines – Clinical research shows these bivalent vaccines protect against both the original SARS-CoV-2 strain and the Omicron variant.

• Novavax COVID-19 vaccine – Studies indicate this option protects against the original SARS-CoV-2 strain.
• The CDC’s COVID-19 vaccination schedule considers variables such as an individual’s age, immune status, and previous vaccinations.

For those aged 6 months through 11 years, the recommended vaccines are age-appropriate formulations of Moderna or Pfizer.

Those 12 years and older may choose between Moderna, Pfizer, or Novavax COVID-19 vaccines according to personal preference and risk factors.

Maintaining an up-to-date vaccination status through additional doses as advised by the CDC’s schedule, helps maximise protection from COVID-19 as more variants emerge.

The CDC recommends staying on schedule based on age, immune status and previous doses received to maintain up-to-date vaccination status. For example:

Kids aged 6 months to age 5

• For children between 6 months and 4 years old, having received three doses of the Pfizer-BioNTech COVID-19 vaccine meets the standard for being up-to-date on their vaccination, as long as at least one of those doses contained the omicron variant strain.
• Five-year-olds who previously received the Pfizer vaccine need only one additional dose containing the omicron variant to be considered up-to-date.
• Between 6 months and 5 years of age, two doses of the Moderna vaccine are sufficient for a child to be up-to-date, provided that their most recent dose included a formulation targeting the omicron variant.

People age 6 and older

• The Centers for Disease Control and Prevention (CDC) recommends that all individuals aged 6 years and older receive at least one dose of a bivalent COVID-19 vaccine containing the omicron (BA.4/BA.5) variant strains. This additional vaccination should be administered regardless of any prior SARS-CoV-2 immunisations.
• According to the CDC, individuals over 6 years old with normal immune function will be considered up-to-date on their COVID-19 vaccinations following one dose of the Pfizer-BioNTech or Moderna bivalent vaccines. Both of these vaccines protect against the original SARS-CoV-2 strain as well as the omicron variants.
• For those aged 12 and older who originally received a two-dose primary series of the Novavax COVID-19 vaccine, completion of that regimen is sufficient to be up-to-date. However, the CDC advises receiving one dose of an updated Pfizer or Moderna vaccine at least 8 weeks after the last Novavax dose for optimal protection against current circulating variants.
• The agency also recommends that individuals who received a single dose of the Janssen/Johnson & Johnson vaccine obtain one dose of an updated Pfizer or Moderna bivalent booster to be considered up-to-date with COVID-19 vaccinations.

People with weakened immune systems

Your healthcare provider may recommend additional doses of COVID-19 vaccine if you have a moderately or severely compromised immune system. For certain high-risk groups, the CDC authorises a primary vaccine series followed by interim and booster doses administered according to an accelerated schedule to provide optimal protection.

Specifically, the agency suggests immunocompromised individuals receive doses of either the Moderna or Pfizer-BioNTech COVID-19 mRNA vaccines at shortened intervals as part of an extended primary series and periodic boosters. Conditions that may warrant this dosing approach include those involving treatment or diseases leading to immunosuppression, such as advanced HIV/AIDS, active cancer therapy, organ or stem cell transplantation, and the use of immunosuppressive medications.

In addition, the CDC recommends a second booster dose for people aged 50 years and older, as well as certain immunocompromised individuals aged 12 years and older. This is due to evidence that immunity wanes more quickly over time in higher-risk groups. Your doctor can determine if you may benefit from an alternative vaccination schedule based on your individual health needs and risk factors.

Vaccination and other actions

Individuals can take several evidence-based steps to reduce their risk of contracting COVID-19 and transmitting it to others. The World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) recommend the following precautions:

• Get vaccinated against COVID-19. Vaccination has been shown to decrease the likelihood of infection and asymptomatic spread significantly.
• Practice social distancing by keeping space between yourself and others in indoor public settings, especially if at higher risk of severe illness. Asymptomatic spread is possible.
• Limit time in crowded indoor areas with poor ventilation. Optimal airflow can help reduce viral transmission risk.
• Perform hand hygiene frequently by washing with soap and water for 20 seconds or using an alcohol-based sanitiser containing at least 60% ethanol.
• Wear a well-fitting face mask in indoor public places during high community transmission. The CDC recommends masks that provide effective source control.
• Improve indoor air quality by opening windows using fans, air filters, and bathroom/kitchen exhausts to dilute and remove airborne particles.
• Cover coughs and sneezes, then wash hands immediately to avoid spreading infectious droplets.
• Avoid touching the face and practice respiratory etiquette to prevent self-inoculation.
• Do not share household items; clean frequently touched surfaces daily to disinfect them.
• Isolate at home if ill and avoid public transportation to reduce exposure to others.

Those with underlying conditions should consult their healthcare provider regarding additional precautions.

Travel

Individuals considering travel should carefully review the latest guidance from public health authorities. Both the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) maintain up-to-date recommendations for safe travel during the COVID-19 pandemic.

The CDC currently advises wearing a well-fitting mask in all indoor public transportation settings, such as commercial flights, buses, trains, and transportation hubs like airports and stations. Face coverings provide an additional layer of protection in enclosed areas where social distancing can be challenging.

Proper hand hygiene should also be practised frequently while in public spaces. Washing with soap and water or using an alcohol-based sanitiser can help reduce the spread of germs.

Those with underlying medical conditions that increase vulnerability to respiratory infections may wish to consult their healthcare provider. Individuals with conditions such as heart or lung disease face a higher risk of complications and should ensure all necessary precautions are taken for safe travel. Regular evaluation of public health guidelines is also prudent prior to travel during periods of elevated community transmission.