COVID-19 disease

COVID-19 disease was detected for the first time in December 2019 in Wuhan, China and classified as a pandemic by WHO on 11 March 2020. By the end of 2021, the cumulative numbers of confirmed cases and deaths had surpassed 200 million and 4 million respectively (last update from 21 September 2021). The economic, political and social impacts quickly became extreme on a regional and global scale. Throughout the pandemic, those facing the greatest vulnerabilities have been the people and groups most neglected by society, including women, children, migrants and refugees. COVID-19 has amplified inequalities, destabilized communities and reversed development gains made in the past decades. An unprecedented level of global coordination and collaboration in health management was and is still needed to tackle the pandemic.

The following are standard case definitions to allow national health authorities to interpret data in an international context. However, during an outbreak case definitions may be adapted to the local context and the Red Cross Red Crescent should use those agreed/established by national health authorities. NB: Consider that during community-based surveillance, volunteers should use broad (simplified) case definitions (referred to as community case definitions) to recognize most or all possible cases, provide relevant risk communication and appropriate actions and encourage them to seek care. Other actors such as healthcare workers or investigators studying the cause of a disease, on the other hand, can use more specific case definitions that may require laboratory confirmation.

Since the beginning of the pandemic, case definitions for COVID-19 have been revised based on updated evidence of the most common and predictive symptoms, clinical signs and transmission dynamics. The case definition below was last updated by WHO in December 2020. Red Cross Red Crescent teams should verify the latest case definition at the time of a particular response intervention.

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus.

Suspected case of SARS-CoV-2 infection:

• A person who meets the clinical AND epidemiological criteria. The clinical criterion is an acute onset of ANY THREE OR MORE of the following signs or symptoms: fever, cough, tiredness, headache, feeling unwell, sore throat, runny nose, difficulty breathing, diarrhoea, loss of smell, loss of taste.
• The epidemiological criteria are residing or working in an area with high risk of transmission of virus; or residing or travelling to an area with community transmission any time within the 14 days prior to symptom onset; or working in any healthcare setting.
• A patient with severe acute respiratory illness.
• Asymptomatic person not meeting epidemiologic criteria with a positive SARS-CoV-2 Antigen-Rapid Diagnostic test.

Probable case of SARS-CoV-2-infection:

• A patient who meets clinical criteria AND is a contact of a probable or confirmed case.
• A person with recent onset of loss of smell or loss of taste in the absence of any other identified cause.

Confirmed case of SARS-CoV-2 infection:

• A person with a positive PCR test.
• A person with a positive SARS-CoV-2 Antigen-RDT AND meeting probable case definition.
• An asymptomatic person with a positive SARS-CoV-2 Antigen-RDT who is a contact of a probable confirmed case.

WHO case definition source of information here:

 https://www.who.int/publications/i/item/WHO-2019-nCoV-Surveillance_Case_Definition-2020.2

An increase in the number of cases of COVID-19 disease above what is normally expected in a population. The specific threshold must be developed based on local epidemiology and immunization programme objectives. The outbreak threshold may, and should, change as the incidence of COVID-19 disease changes. 

In countries with no recent COVID-19 cases reported, a single case should trigger a detailed case investigation. 

• Prolonged unprotected contact with a COVID-19 positive person. This person does not necessarily need to have symptoms.
• Close contact with a distance less than one metre to a COVID-19 positive person.
• Any non-immune person (who has not been vaccinated or previously infected or was vaccinated but did not develop immunity) can become infected.
• Overcrowded areas where physical distancing, proper ventilation and/or wearing a mask is not possible facilitates person-to-person spread.

Attack rates will vary from one outbreak to another. In case of an outbreak, consult the latest information provided by health authorities.

Due to the ongoing COVID-19 pandemic, the estimated attack rate may change over time, and will vary location by location depending on natural and vaccine-derived immunity and potential new variants of SARS-CoV-2. Current estimates place the overall attack rate around 45 per cent.

• People aged 60 years and over.
• People with underlying medical conditions such as high blood pressure, cardiovascular disease, diabetes, chronic respiratory disease, chronic kidney disease, chronic infectious diseases, cancer and obesity.
• People who are immunosuppressed.
• People who smoke.

SARS-CoV-2 virus and variants.

While not confirmed, the most likely reservoir hosts for SARS-CoV-2 are fruit bats (common hosts for many other coronaviruses). Other animals known to be susceptible to infection include ferrets, cats, dogs, voles, hamsters, white tailed deer and humans. To date COVID-19 outbreaks have been reported among at least 17 species worldwide.

Droplet spread: The virus is spread through droplet infection by coughing, speaking or sneezing.

Airborne transmission: An aerogenic transmission can also take place through dust and droplet nuclei (droplets ≤5 μm) which are able to travel longer distances and stay in the air for a longer period.

Contact transmission: In rare cases, the virus can be transmitted through fomites on surfaces touched prior by infected people or by close skin-to-skin contact with infected people. The virus can then spread when touching the nose, mouth or eyes after touching the contaminated surface.

On average five days, however there is evidence of as little as three days to up to 14 days.

2.5 days before symptom onset until 9 days after symptom onset; highest infectivity takes place just before and around symptom onset.

Most common symptoms: fever, cough, tiredness, loss of taste and smell.

Less common symptoms: sore throat, headache, aches and pains, diarrhoea, a rash.

Serious symptoms: difficulty breathing or shortness of breath, loss of speech or mobility, chest pain.

Influenza, pertussis, other acute respiratory infections (e.g. pneumonia), exacerbated chronic respiratory diseases, allergies.

Authorized assays for viral testing include those that detect SARS-CoV-2 nucleic acid or antigen with sample material from the respiratory system such as nasal or oral swabs. Some tests are point-of-care tests, meaning results may be available at the testing site in less than an hour. Other tests must be sent to a laboratory to analyse, taking several hours or days (depending on the capacity of the laboratory).

Please refer to the appropriate local or international guidelines for clinical management. All clinical management including the administration of any treatment or vaccine should be conducted by health professionals.

• Different vaccines exist since December 2020 around the world to prevent COVID-19 disease. The number of vaccines and the timespan in between doses is updated by WHO and the national ministries of health as new studies are published revealing new information about this recent disease. New variants might emerge in the future.
• In case of serious symptoms: hospitalization is required. Oxygen support up to advanced respiratory support such as ventilation might be necessary. This is usually associated with the administration of medication.
• Several antiviral pills have also become available for emergency use in some countries. When identified and prescribed early (within the first few days of infection), these can reduce severe disease in at-risk individuals with known COVID-19 infection.
• In case of mild symptoms: initially no requirement for hospitalization and only symptomatic therapy in isolation. This means staying home, limiting contact with others through physical distancing, wearing facemasks when around others, using separate bedroom and bathroom if possible. Signs and symptoms may worsen, which is why a regular update of the patient’s clinical presentation is needed.

• Immunity after infection has passed is estimated to last around six months.
• Population immunity varies by disease and happens as a result of vaccination or through immunity developed through previous infection. Information is still emerging on how many people need to be vaccinated against COVID-19 before the population can be considered protected and on the number of booster vaccinations necessary.