COVID-19 is caused by SARS-CoV-2, a human coronavirus first identified in December 2019. SARS-Cov-2 is an RNA virus and as a result it acquires mutations quickly. Often, new mutations occur that have no impact or may be detrimental to the virus. Occasionally, these mutations result in a competitive advantage against other versions (lineages) of the virus that are circulating. When this occurs, that lineage may become more prevalent in the population. If one of these lineages or groups of lineages have characteristics that impact public health (increases in severity, transmissibility, or evasion of existing immunity; resistance to therapeutics), those lineages may be considered a variant of concern or interest. The CDC and WHO track SARS-CoV-2 variants for mutations that might lead to therapeutic resistance or reduced vaccine efficacy. For more information visit: https://www.cdc.gov/coronavirus/2019-ncov/variants/index.html.
Symptoms commonly reported among adults with COVID-19 include:
Signs and symptoms of COVID-19 in children vary by age of the child and are usually milder compared to adults.
See the ISDA Real Time Learning Network for a more detailed discussion of COVID-19 clinical signs and symptoms including severity of illness categories.
Case Classification
Outbreak case classification may differ by sector. Please refer to setting-specific B73 chapters for further information about case classification.
There are three principal ways in which infectious exposures to respiratory fluids carrying SARS-CoV-2 occur:
Inhalation plays a larger role than previously believed, as aerosolized particles can remain in the air for minutes to hours. This is more likely in enclosed spaces with poor ventilation, especially if an infectious person spends an extended period in that space or if they are participating in activities that increase exhalation of respiratory fluids, such as vigorous exercise, singing, or shouting.
For CDC patient-friendly information, see How COVID-19 Spreads.
People with SARS-CoV-2 infection are likely most infectious in the first 5 days of illness. Most otherwise healthy individuals will have stopped shedding the virus by the 10th day after symptom onset.
Isolation duration and requirements for COVID-19 cases and close contacts vary by setting. See setting-specific B73 chapters for details.
See the ph.lacounty.gov/covidtherapeutics and the NIH COVID-19 Treatment Guidelines for comprehensive information on the medical management of COVID-19 prepared by the COVID-19 Treatment Guidelines Panel. Providers should make treatment decisions based on currently available evidence.
For patient-friendly information about COVID treatment please refer to: http://publichealth.lacounty.gov/acd/ncorona2019/medication/.
Refer to the CDC Guidelines to determine when a person is considered up to date with their COVID-19 vaccines. Staying up to date is safe and important for everyone because it can increase prior protection (from previous vaccination or infection) that may have decreased over time. For local resources including information on where the vaccine is available visit VaccinateLACounty.com.
Clinical and epidemiologic histories are required to aid in diagnosis. Direct viral detection methods with sensitive molecular tests (e.g. RT-PCR) are recommended for diagnosing current infection with SARS-CoV-2. Antigen tests and over the counter (OTC) self-tests can also be used to diagnose acute infection but are less accurate than PCR tests.
When using lower sensitivity assays (e.g., antigen tests, some molecular tests, OTC self-tests), negative results are considered presumptive and confirmation with RT-PCR is recommended, especially if important for clinical management or infection control.
Serological testing is not a standard part of outbreak investigation.
See CDC Testing for SARS-CoV-2 Infection for an overview of test types.
Facilities are encouraged to test through a commercial lab. Facilities should follow the specimen collection and pick-up instructions as per the facility’s designated commercial clinical laboratory. They should work directly with the clinical laboratory for all questions regarding specimen collection and transport.
PHL SARS CoV-2 PCR Specimen Collection
Upper Respiratory Specimen--for initial diagnostic testing, collect at least one upper respiratory specimen.
Any of the following specimens are acceptable:
Swabs: Acceptable swab types include synthetic fiber swabs (flocked or spun polyester) with plastic or wire shafts. Do not use calcium alginate swabs or cotton swabs with wooden shafts. Place swab in a minimum of 1-3 mL viral transport media, liquid Amies, or saline.
Storage: Refrigerate specimens at 2-8°C and transport on cold pack. If specimen storage exceeds 3 days, freeze specimen at ≤ -70°C and ship on dry ice.
Los Angeles County PHL Test Request Form: http://www.publichealth.lacounty.gov/lab/labforms.htm
For more information see:
A patient with a history of recent recovery from COVID-19 is defined as a person with a positive viral COVID-19 test within the past 3 months (90 days) who has recovered from the previous infection. Recovered means they are no longer considered infectious (i.e., their isolation period has ended).
If the patient had symptoms with their most recent infection, the 90 days are from the onset of the initial COVID-19 symptoms. If they never had symptoms, then the 90 days are from the date of collection of the first positive viral COVID-19 test.
If the recently recovered person
Is asymptomatic
Develops new symptoms consistent with COVID-19 illness
Rationale:
Immunocompetent patients who have recovered from acute COVID-19 infection can continue to have detectable SARS-CoV-2 RNA in upper respiratory specimens for 3 months after illness onset and persistent positive antigen tests are possible for at least 24 days. Replication-competent virus has not been reliably recovered from such patients, and they are not likely infectious.
Antigen testing of asymptomatic close contacts is recommended to identify a new infection if 31-90 days have passed since their first positive test. This is because persistent antigen positivity is unlikely after a month and because the probability of SARS-CoV-2 reinfection increases with time due to exposure to viral variants and waning immunity.
See the appropriate B73 chapters for setting-specific control measures, including control of cases and contacts.
Public Health has made reasonable efforts to provide accurate translation. However, no computerized translation is perfect and is not intended to replace traditional translation methods. If questions arise concerning the accuracy of the information, please refer to the English edition of the website, which is the official version.
