COVID-19 Basics: What you should know

Updated Mar. 2, 2022

UC Davis Health is committed to providing you with the most up-to-date information on COVID-19, including the latest on testing, how COVID-19 is spread, and COVID-19 vaccines. Learn more about the virus so you can better protect yourself and your family:

The novel coronavirus (COVID-19), which originated in Wuhan, China, is part of a family of viruses that our care teams are very familiar with. Coronavirus cause respiratory tract infections, including the common cold, and more serious infections like SARS. Symptoms start out like any other cold: fever, runny nose, cough and overall just feeling bad. It can progress and cause more severe illness like pneumonia, which can be fatal.

Evidence shows novel coronavirus is most often transmitted through droplets generated by coughs and sneezes. COVID-19 may also be transmitted when people touch contaminated surfaces and then touch their face, nose or mouth.

COVID-19 symptoms may appear 2-14 days after exposure to the the virus, according to the CDC. People with these symptoms or a combination of symptoms may have COVID-19:

  • fever or chills
  • cough
  • shortness of breath or difficulty breathing
  • fatigue
  • muscle or body aches
  • headache
  • diarrhea
  • new loss of taste or smell
  • sore throat
  • congestion or runny nose
  • nausea or vomiting

Call your primary care provider if you experience COVID-19 symptoms and believe you've been in close contact with a person who has the virus.

Learn more about which COVID-19 symptoms you should watch for

This variant was first classified and named omicron on Nov. 26 by the World Health Organization (WHO). Omicron was first discovered in South Africa. The variant has more mutations than any other variant that researchers have discovered. Many of the mutations are in the spike protein, which is what attaches to the cells and relates to how the virus is spread.

For this reason, all vaccines being used are focused on targeting and developing an immune response to the spike proteins. Health experts recommend that we all continue to help stop the spread of COVID-19 by being fully vaccinated, wearing a mask, staying home if you’re sick, washing your hands, and keeping your physical distance when around others.

Learn more about the omicron variant from UC Davis Health

Learn more from the omicron variant fact sheet from the California Department of Public Health

You can find a COVID-19 testing location near you through California’s COVID-19 website. You can view  county testing resources as well:

UC Davis Health patients and non-patients with COVID-19 symptoms can contact a doctor through UC Davis Express Care or by contacting your primary care provider by phone or MyUCDavisHealth. A doctor can help quickly coordinate a COVID-19 test, possibly at a UC Davis Health drive-up site in Sacramento, which are available seven days a week.

Access UC Davis Express Care for patients

Access UC Davis Express Care for non-patients

Healthy Yolo Together, a public health project of UC Davis, also provides free saliva-based COVID-19 testing at locations in Yolo County.

Read more from UC Davis Health: More options than ever for at-home and community COVID-19 tests

We don’t really know what the presence of antibodies means. It doesn’t necessarily mean that you’re immune to the coronavirus. Science has yet to determine what level of antibodies confirm immunity, if immunity is possible, or how long immunity might last. The result of a positive antibody test means nothing given the current gaps in knowledge about COVID-19. Until there is more definitive information, we should assume, even with positive antibodies, that a person may still be susceptible to the coronavirus.

You can get COVID-19 even after previous infection. Reinfection is rare within 3 months of initial infection, but immunity decreases over time. For an unvaccinated person after recovery from COVID-19, vaccination is recommended which reduces the risk of reinfection by more than 50%.

Common COVID-19 treatments include remdesivir, convalescent plasma, and dexamethasone. Remdesivir and convalescent plasma are used to control viral infection, and dexamethasone is used to control the immune response to infection. These drugs have often proven more successful than using a ventilator, which sometimes has made lung inflammation worse.

Learn more about COVID-19 treatments

Yes, UC Davis Health is conducting multiple clinical trials related to novel coronavirus research. Those include an experimental treatment using the antiviral medication remdesivir for patients hospitalized with severe COVID-19 infection. If you are interested in participating in a COVID-19 clinical trial, visit the UC Davis Health Clinical Studies page.

COVID-19 prevention

Vaccinations are available for anyone ages 5 and older. You can schedule first, second, and third or booster doses at UC Davis Health through MyUCDavisHealth or the state of California's MyTurn.ca.gov. UC Davis Health patients can also schedule an appointment by calling 916-703-5555 Monday-Friday 8 a.m.-5 p.m.

UC Davis Health is vaccinating patients and non-patients at our primary care clinics in:

  • Auburn
  • Carmichael
  • Davis 
  • Elk Grove
  • Folsom
  • Rancho Cordova
  • Rocklin
  • Roseville
  • Sacramento

Learn more about how to schedule your COVID-19 vaccine and what to expect

Learn more about COVID-19 vaccines for kids ages 5 to 11

The CDC and FDA recommend a third dose Pfizer or Moderna COVID-19 vaccine or booster dose for the following groups:

  • people with compromised immune systems ages 5 and older. Pfizer is the only approved vaccine for ages 5-17. This group is also eligible for a fourth vaccine booster five months after their third dose.
  • people ages 12 and older. Pfizer is the only approved vaccine for ages 12-17.

Additionally, anyone who received a Johnson & Johnson vaccines is eligible for a second vaccine dose.

Schedule your booster or third dose through MyUCDavisHealth or California's MyTurn.ca.gov.

Learn more about COVID-19 booster shots and third doses

Yes. It’s important to know for several reasons:

  1. If your illness progresses, you’ll want to know so you can take advantage of treatments.
  2. You need to know whether to isolate so you can reduce your chances of infecting others, especially those who are more vulnerable to severe COVID-19.
  3. You will want to notify your loved ones and contacts so they can monitor themselves for COVID-19 symptoms and get tested if appropriate.

Learn what to do if you test positive

If you've been fully vaccinated against COVID-19 and have no symptoms, you do not need to quarantine if you've been in close contact with someone with COVID-19. Vaccinated people should get tested 5-7 days after close contact with a COVID-positive person, even if they have no symptoms. 

If you have not received a COVID-19 vaccine, the CDC recommends that you quarantine for 5 days after you've been exposed to someone who tested positive for COVID-19. You should then also wear a mask for an additional 5 days after your quarantine period is complete. You should also get tested to determine if you have COVID-19.

You should remain on the lookout for any COVID-19 symptoms for 14 days after exposure.

CDC explains what to do in quarantine and isolation

Learn more about recovery at home if you test positive for COVID-19

Yes. You can get reinfected after having COVID-19, although it is less common in the first 90 days after infection. The vaccines are not 100% effective, and breakthrough infections may occur.

However, if you have had COVID-19 and are then vaccinated, this decreases your chance of reinfection by about half. Also, protection wanes over time, which is why boosters are important. This is especially true for front line workers and those who are higher risk of complications, such as those with diabetes and respiratory illnesses.

A recent study based on data from Israel's first two coronavirus waves showed a connection between vitamin D deficiency and COVID-19 severity and death rates. The study took place before COVID-19 vaccines were widely available. It found that people who were low on vitamin D were more likely to develop a severe or critical case of COVID-19, compared to people who had higher levels of vitamin D in their blood.

Patients with vitamin D deficiency were 14 times more likely to have a severe or critical case of COVID-19. Additionally, the death rate for those with low vitamin D levels was 25.6%, compared with 2.3% among those with adequate levels of vitamin D.

Vitamin D plays a role in the body’s immune system and is known to enhance the function of immune cells. In this case, vitamin D slows some of the inflammation that can make COVID-19 more severe.

Most vitamin D comes from direct sunlight on the skin. It's also found in foods such as fatty fish, egg yolks, and fortified dairy products. Mushrooms are one of the few non-animal sources of vitamin D.

Learn more about the link between vitamin D levels and COVID-19

Health professionals recommend that you wear a face mask (covering both the mouth and nose) when indoors around anyone not in your household and outdoors in crowded settings. To protect against omicron, health experts are recommending that you upgrade your face mask to an N95 or KN95 for more protection.

Several studies have indicated how effective masks can be in protecting yourself and others. It’s important to remember that you may be asymptomatic and not know you are infected but still able to spread COVID-19. Masking up in these situations helps protect vulnerable people you could unknowingly infect.

Learn which face masks protect you the best against COVID-19

It’s difficult to estimate the protection from cloth masks since they aren’t standardized, but some studies suggest they are about 50% effective, compared to 60-70% for surgical masks and 95% for N95s. There is strong evidence that properly worn N95 masks are the most protective in terms of blocking transmission.

Cloth masks alone are not very effective against the most transmissible variants like omicron. If an N95 mask is not available, a surgical mask covered with a cloth mask can be very effective.

Learn which face masks protect you the best against COVID-19

Human hands have a lot of microbial, built-in defenses in the skin. COVID-19 can largely survive longer on gloves than it would on hands.

Don’t rely on gloves as a barrier to coronavirus, as your hands are probably more resistant to the virus than the gloves are. What’s most important is hand hygiene and not using your hands (gloved or not) to spread virus to your mouth, nose, eyes or ears.

You can reuse gloves – although they are inexpensive, and it’s recommended to use a new pair each time. However, the virus doesn’t last forever on a surface. After 7 days, the chance of the virus infecting you is very low. You can sanitize gloves with alcohol or wash them with soap and water.

COVID-19 and children

The Pfizer vaccine has received emergency use authorization from the U.S. Food and Drug Administration (FDA) for children ages 5-17.

Pfizer is the only approved vaccine for children ages 5-17. For those who are under 18 years old, they will need to have a parent or legal guardian provide consent for treatment at their appointment. UC Davis Health accepts written or verbal consent. It's also advised that anyone under age 18 have someone drive them to and from their appointment. With any vaccine, there's an increased risk of fainting for children ages 11 to 18, according to the CDC.

Get your questions answered about kids and COVID-19 vaccines

Learn more about how the COVID-19 vaccine works

Since May 2020, the CDC has been tracking multisystem inflammatory syndrome (MIS-C) in children. It is a rare but serious condition that can be life-threatening and require hospitalization, according to the California Department of Public Health. Some children developed MIS-C after being diagnosed with COVID-19 or after coming into contact with someone who had COVID-19.

According to the CDC, most cases are in children between the ages of 1 and 14 years. Children typically developed MIS-C 2-4 weeks after being infected with COVID-19. Symptoms of MIS-C include:

  • fever that doesn't go away
  • abdominal pain
  • vomiting
  • diarrhea
  • neck pain
  • rash
  • bloodshot eyes
  • feeling tired

Contact your child's physician immediately if your child has these symptoms.

Most infections that happen in a family are when an adult brings COVID-19 home and infects their children. Several studies suggest that about 90% of household infections are from adults infecting children. Only about 10% are children infecting adults.

Generally, younger children don’t get severe COVID-19 like older children and adults. However, many children have been hospitalized with COVID-19. Sometimes children can end up getting long COVID, which can interfere with the clarity of their thinking and their memory. Sometimes when they get long COVID they’ll need to miss school, which can also affect their brain development.

There are other rare side effects of getting COVID-19. Sometimes children can have actual infection and inflammation of their brains because of the virus, which has led some children to be hospitalized. Although that’s rare, it can occur.

Read about children and COVID in this Q&A with a UC Davis pediatric infectious disease expert

Learn more about long COVID and lasting symptoms

Even children who are asymptomatic for COVID-19 can have long COVID. That's why preventing all cases, even the cases where children show no symptoms, is important. Pediatricians encourage parents to have their children vaccinated if they’re eligible. The next best protection is wearing a mask.

Learn more about long COVID and lasting symptoms

Multisystem inflammatory syndrome in children (MIS-C) generally shows about 2-4 weeks after acute COVID-19 infection by 2-4. The most common symptoms are high fever, rash, and gastrointestinal issues such as nausea/vomiting/diarrhea, although many other systems in the body may be involved. The most common age for MIS-C is 5 to 13 years old, and these children tend to be very ill.

Respiratory syncytial virus (RSV) usually causes upper respiratory symptoms such as runny nose, sneezing, runny eyes, cough, and low-grade fever. It's generally mild except in children under 2 years of age, where it can trigger bronchiolitis, an inflammation of lung airways that may lead to wheezing.

Flu generally has an abrupt onset of high fever and respiratory symptoms such as runny nose and cough, plus muscle aches, fatigue and tiredness. Gastrointestinal symptoms commonly occur in children including abdominal pain, nausea, vomiting, and diarrhea.

Read more: Why MIS-C is a life-threatening COVID-19 complication that parents don’t want to miss

Your health and medical care

If you need to go to the hospital because you are having a medical emergency, call 9-1-1 or get to a hospital immediately. If you have COVID-19 symptoms that are difficult to manage, but not that serious, call your primary care provider or seek urgent care.

If you have symptoms that seem like a common cold, but aren’t that serious, isolate yourself, treat it at home, and stay away from others.

Note: Some people are considered at higher risk for severe illness from COVID-19, according to the CDC. Some of these groups include people over age 65, and people of any age who have serious underlying medical conditions such as diabetes, chronic lung disease, serious heart conditions, or cancer treatment. The CDC currently advises higher-risk groups to:

  • Consult with your health care provider for more information about monitoring your health for symptoms suggestive of COVID-19
  • Have a plan for if you get sick, and
  • Call your health care provider if you do get sick

The CDC also posts specific information about other populations who need extra precautions, such as pregnant women and racial and ethnic minority groups.

If your COVID-19 symptoms or medical condition are serious enough that you need medical assistance, call your doctor, health care provider, advice nurse, or other health care professional. 

Learn how to make your appointment a video visit

Yes, please don't delay care. As in any hospital, there are many infection control and management measures in place at all times. We manage infectious disease, like COVID-19, every day in the hospital. We are here to care for everyone and to make sure everyone gets excellent care.

Visitors at UC Davis Medical Center:
Currently, we are restricting visitors within UC Davis Medical Center in order to help keep COVID-19 out of the hospital. Read more about our visitor restrictions

To reduce the spread of COVID-19, we are limiting the number of caregivers who can accompany patients during appointments at our clinic and medical office locations.

Learn more about our caregiver policy for outpatient clinics.

When people visit us in person, we’re asking everyone questions as they enter the buildings. We’re screening for COVID-19 symptoms at entrances to all of our clinical locations, including our hospital, our outpatient centers, and our medical offices.

Our care teams are handling COVID-19 cases in much the same way we manage other diseases that require safety precautions and monitoring. We are in constant communication with the CDC, California Department of Public Health and Sacramento County Public Health about managing potential cases.

The information we receive includes best clinical practices for enabling clinicians, as well as patients and the public, to avoid being exposed to the virus.

Every person entering our care facilities is screened daily and required to report whether they have, or have recently experienced, specific kinds of symptoms. This is one of many ways we are making sure our health care workers are well and ready to carefully care for you.

Any employee with illness symptoms is expected to stay home until they are no longer contagious. It is in everyone’s interest to keep our workforce as safe and healthy as our patients.

Stay informed!

Receive updates on COVID‑19 and more

View past newsletters