WHO guidelines to improve our understanding of COVID-19

The best way to stop a new disease from spreading is to identify the very first cases (index cases) that showed up in a setting - primary cases - and to quickly identify all the people who have come in contact with the original case. The more the contacts identified, the lesser the chance of the disease spreading in the community.

A close contact is anybody who has been within a metre of the primary case after they show symptoms and at least 4 days before they show symptoms. The person does not have to be in physical contact with the patient to be listed as close contact. Close contacts may include the immediate family, neighbours, colleagues, teachers, classmates or anybody in the patient’s social sphere. 

A primary case may be imported - had come from a country with a high number of cases within the last 14 days. However, it is defined as the first case that shows up anywhere in a setting it could be a single household, a healthcare facility or a workplace. 

Anyone who develops symptoms of the disease or tests positive for it within a day (or more) after coming in contact with the primary case is known as a secondary case.

If someone is asymptomatic or showing the signs of COVID-19 (fever, cough) but has a history of travel to the affected area or coming in contact with an infected person is listed as a suspected case. Listing of suspected cases is done for ease for tracing them later.

Read more: How to take a suspected COVID-19 patient to the hospital

A probable case is someone who has got inconclusive results in a COVID-19 test. And those that do get a positive result in COVID-19 test are confirmed cases.

To find out suspected and confirmed cases, respiratory samples, blood and other fluids (if needed) are taken from all the close contacts of the primary patient on day 1 and then again between day 14 to 21. The contacts are followed up to look for symptoms between this time. If any person gets symptoms or tests positive, they are shifted to confirmed cases. Confidentiality is maintained regarding the names of all close contacts throughout the investigation.

Read more: What is contact tracing and how does it help in curbing COVID-19

Tracing the first case and its close contacts: 

• Helps understand the clinical presentation of the diseases in various people.
• Helps find out the incubation period of the disease. Incubation period is the time between exposure to the virus and manifestations of symptoms.
• Gives information about the modes of transmission of the disease.
• Tells about the rate of secondary infections (how quickly the infection spreads amongst close contacts) and the features of the disease in the secondary cases.
• Helps identify the reproductive number of the disease - how many people a single person can infect - and the serial interval - the time period between two subsequent infections.
• Helps check for the severity ratio of the disease - how many cases are mild and how many are fatal.

To identify all the imported cases, the National Centre for Disease Control also has a self-reporting/case investigation form for those suspected of having symptoms of COVID-19. The form includes all the personal information of the person - name, address, contact number, age and gender for example, along with symptoms, risk factors (in case the patient has a disease) and a travel history to the affected areas. Also, the forms for contact tracing.

Some of the findings that are reported in this study include:

• The number of primary cases and their close contacts.
• Number of symptomatic, asymptomatic, suspected and laboratory-confirmed cases amongst contacts.
• Close contacts who already have developed antibodies to the virus.

All the findings are stratified as per characteristics like age, sex, time, and place. 

As the name suggests, this is done to check for the spread of COVID-19 within a household. A household transmission data is collected to compliment the contact tracing data and to reinforce its findings. 

However, it particularly helps in:

• Finding out the incubation period, serial interval and the reproductive number of COVID-19.
• Identification of the proportion of symptomatic and asymptomatic cases.
• Finding out the high-risk groups.
• Checking for how long the infected person sheds the virus and for how long is he/she infectious.
• Studying the pattern of healthcare in different subgroups.

To conduct this study, all the household members of the confirmed patient will be tested four-time within a period of 28 days. Respiratory samples are taken on day 1, 7, 14 and 28. Blood/serum samples are taken on day 1 and 28 (maybe on day 14 too) and symptom diaries are prepared for all the members for the whole period (more importantly for the first 14 days).

Read more: Home-based care for COVID-19

Some of the following things are reported in this study:

• Total number of household members of the primary case and the number that is tested positive for COVID-19.
• Number of members that already have antibodies to the infection in their blood.
• Number of symptomatic and asymptomatic members.

Healthcare workers dealing with COVID-19 play an important role in preventing the transmission of infection. However, since they come constantly in contact with infected patients, it is important to assess the risk of them developing the disease and the possibility of adverse outcomes.

The study mainly includes the healthcare workers who come in direct contact with confirmed patients or those who come in contact with the body fluids of the patient or any instrument or device that is considered to be contaminated - anything that has body fluids from the patient or has been used by on the patient.

This study helps to fulfil the following objectives:

• Checking the risk of infection in healthcare workers and to look for the range of clinical presentations.
• To evaluate the efficiency of personal protective equipment used by healthcare workers in a clinical setting.
• Finding out how quickly the disease spreads among healthcare workers. This is done by finding out the secondary infection rate for contacts of healthcare workers at an individual level.
• To check the efficiency of infection control programmes at the level of the health facility and at the national level.
• To study the serological response (changes in the levels of COVID-19 antibodies in the serum of the patient) of the person’s body against the infection.
• Identify the possible transmission routes.

Read more: How does COVID-19 spread

For the study, all the data including the contact with the confirmed case, use of personal protective equipment (PPE) and clinical symptoms (if they show up in a healthcare practitioner) are noted.

Respiratory samples are taken for diagnosis of the disease and serological (blood/serum) samples are taken to study immune response (formation of antibodies).

Reports in this study include some of the following details too:

• The role of healthcare workers who have been tested positive for COVID-19. Are they doctors, nurses, or any other member of the staff.
• How many household members of the confirmed case of healthcare practitioners have got positive results. These cases can be stratified by age, gender, and the role of the healthcare practitioner in the hospital like mentioned above.

Read more: 10 steps to put on personal protective equipment for healthcare practitioners

So far, all the statistics and data including the mortality rate of COVID-19 is mostly based on severe cases. Not much is known about the asymptomatic and mild cases and how much of a share they have in the total number of infected cases. Assessing the serological data of the general population (looking for the presence of COVID-19 antibodies in their blood) would help to give an estimate of such cases too along with the severe cases. This, in turn, would aid in getting a better understanding of the extent of infection in the community. It would also provide a better understanding of the mortality rate of the disease.

Since this study involves age-stratification, it provides a clear picture of the infection rate. Furthermore, risk factors of COVID-19 can be assessed through this data.

For the study, populations should be chosen from both high incidence and low incidence areas.

The data can be collected through cross-sectional (assessing data from a group of people at a specific point of time) or longitudinal studies (assessing data from a population or a group of individuals over a period of time).

Reporting in this study involves the following:

• The total number of individuals in the study including their age and sex.
• At what time the sample was collected during the outbreak.
• The number of people who have antibodies for COVID-19 and are symptomatic or asymptomatic.

Read more: Mild vs Severe cases of COVID-19

Since COVID-19 spreads through droplets, it is important to determine for how long the virus can stay on various surfaces. This study also helps to check the role of environmental contamination in the transmission of COVID-19 and hence helps better in contact tracing.

For the study, samples are obtained from all the high touch surfaces in and around the ward where a confirmed COVID-19 patient is in - this includes both healthcare and household settings. The study is done for up to a week after the patient has left the ward or the location of sampling.

The WHO recommends the following sample collection sites to study COVID-19 fomites and environmental transmission in a healthcare setting:

• Ambulance - the wall beside the stretcher of the patient, the handlebar and the ceiling of the ambulance, and the inside of the blood pressure cuff. 
• Ventilation exits and air purifier filters wherever the patient has passed through. This includes the entrance, corridors, waiting room and the patient’s room.
• Doorknobs, keyboards, light switches, sinks, faucets and clothing in case a hospital staff member is a possible route of infection.
• Patient’s bedding, IV pole, the stethoscope used to check the patient, their thermometer, soap dispenser, cups, curtains, garbage bin, or basically anything that has come in contact with the patient or their body secretions.  
• To determine how far the virus can go samples from all the things in less than a metre, 2 metres, 3 metres (and so on) from the patient are taken.

This study also involves data on any procedure that is likely to generate aerosols and the details of disinfection in all the suspected areas including how frequently disinfection is done, the time of disinfection and the details of disinfectant.

Aerosoles may be generated by procedures like bronchoscopy (an endoscopic procedure that is used to visualise the inside of airways), sputum suction (a suction machine and tube are used to remove excess mucous from the airways and to keep the person’s airways open), chest physiotherapy and endotracheal intubation (pushing a tube through the mouth into the airways to keep the airways open).

The reported from these findings also include the following:

• The number of locations from where samples are taken and how are they related to the patient.
• How many patients were in and around the location when the sample was taken.
• How many samples were collected.
• How many samples had RNA of the virus and how many samples have the whole and viable virus.