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Published on: Jul 09, 2020
2 minute read
By: Dr Rakesh Choudhary

COVID- 19 Tests – What Do You Need To Know?

COVID- 19 tests – What do you need to know?

Author: Dr. Rakesh Choudhary MBBS, MS, FRCS UK, FRCS Orth UK, MChOrth UK.

Dr. Choudhary is a practicing consultant surgeon in the UK.

So many of us think it is not their job to learn about COVID-19 tests and this should be left for the experts and governments to decide about these tests. But I strongly suggest the public must have a basic understanding of these tests which they may have to have themselves.

Basically there are two types of tests, one which can detect the virus in the body and the other one which tells if the person had the previous infection.

Virus test

The virus test detects an active infection. It detects the genetic material (RNA) of the virus during an active infection. It is also called a PCR (polymerase chain reaction) test or nucleic acid test and is sometimes inaccurately called an antigen test.

A swab is taken from deep in the back of your throat and deep in the nose. The swab should go deep up to 7-8 cm and is generally uncomfortable for the patient. Swabbing patients using the correct technique is paramount in ensuring an accurate result. By simply swabbing the inside of the nasal passage is not deep enough to verify that the virus is present.

What does virus testing tell you?

This test tells us if a patient is actively infected with the COVID-19 virus. Virus testing is used mainly for the diagnosis of COVID-19.

When should it be done?

The virus test works best during the first seven days of symptoms.

The coronavirus can be detected in swabs even before symptoms of illness first appear . This is why people can be infectious for a few days before the onset of symptoms, which usually appear about 5 days after the virus infects. Some people have no symptoms throughout their infection but are positive on the virus test and infectious to others. After a few days of illness, the concentration of the virus falls (as seen in swab samples) and the symptoms of the illness usually recede.

Accuracy of the test

In a person with COVID-19, the test is less likely to give a positive result late in the course of infection once the virus has been cleared by the immune system, or if an inadequate sample is taken from the nose or throat. There are concerns that the rate of ‘false negative’ test results could be as high as 30% and a significant number of people are wrongly being told they do not have the virus.

Antibody test

Antibody tests check your blood by looking for antibodies, which may tell you if you had a past infection with the virus that causes COVID-19. Antibodies are protein structures that are produced by the immune system in response to certain infections. The antibody can help fight off infections and can provide protection against getting that disease again (immunity). Antibodies are disease-specific. For example, measles antibodies will protect you from getting measles if you are exposed to it.

The antibody test detects the presence of antibodies as a marker of past infection. The antibody test (blood test) will only detect infections after the immune system has produced antibodies that recognize the virus. This happens approximately 7–10 days after symptoms develop.

Tests carried out a week after a patient develops symptoms will detect only 30% of people who had COVID-19 infection. Accuracy increases to 72% at two weeks and to 94% in the third week. Some people may take even longer to develop antibodies, and some people who are infected may not ever develop antibodies.

Interpretation of the antibody test is complex for non-medical people. Basically having antibodies to the virus that causes COVID-19 may provide protection from getting infected with the virus again. If it does, we do not know how much protection the antibodies may provide or how long this protection may last.

Read Blog

How Cold Weather Affects Health: Understanding Winter’s Impact on the Body

Seasonal changes influence human health more than most people realise. Cold weather, in particular, places unique stress on the body and can worsen existing health conditions while increasing susceptibility to new illnesses. Understanding how cold weather affects health is essential for preventing seasonal complications and maintaining wellbeing during winter months.

In India, winter-related health issues vary by region but commonly include respiratory infections, cardiovascular strain and joint discomfort. According to the Indian Council of Medical Research (ICMR) and World Health Organization (WHO), cold exposure is associated with increased morbidity, especially among older adults and people with chronic conditions.

Why Cold Weather Impacts the Body

The human body works constantly to maintain core temperature. In cold environments:

blood vessels constrict to conserve heat
energy expenditure increases
immune responses may weaken
organs work harder to maintain balance

These adaptations, while protective, also create health vulnerabilities.

Increased Risk of Infections

Weakened Immune Response

Cold weather can suppress immune function, making it harder for the body to fight infections.

Factors contributing to winter infections include:

reduced vitamin D due to less sunlight
dry air affecting mucosal defenses
closer indoor contact

Common winter infections include colds, flu and respiratory illnesses.

Respiratory Health Problems

Cold air irritates the respiratory tract.

This can lead to:

worsening asthma symptoms
bronchitis flare-ups
increased cough and breathlessness

WHO reports higher hospital admissions for respiratory illnesses during colder months.

Impact on Heart Health

Cold temperatures affect cardiovascular function.

Blood Vessel Constriction

Cold causes blood vessels to narrow, increasing:

blood pressure
heart workload

This raises the risk of:

heart attacks
strokes

People with existing heart disease are particularly vulnerable.

Joint and Muscle Pain

Cold weather affects musculoskeletal health.

Common complaints include:

joint stiffness
muscle aches
worsening arthritis pain

Lower temperatures reduce joint lubrication and increase sensitivity to pain.

Metabolic and Weight Changes

Winter often leads to:

reduced physical activity
increased calorie intake
metabolic slowdown

These changes contribute to weight gain and worsen metabolic conditions such as diabetes.

Skin and Hydration Issues

Cold air holds less moisture.

This leads to:

dry skin
cracked lips
worsening eczema

Dehydration is also common as thirst perception reduces in cold weather.

Mental Health Effects

Seasonal changes can influence mental wellbeing.

Cold weather is associated with:

low mood
reduced motivation
seasonal affective symptoms

Limited sunlight affects circadian rhythm and serotonin levels.

Cold Weather and Older Adults

Elderly individuals face higher risks due to:

reduced temperature regulation
weaker immunity
existing chronic conditions

Winter-related complications are a significant cause of hospitalisation in older populations.

Why Chronic Diseases Worsen in Winter

Conditions such as:

hypertension
arthritis
asthma
diabetes

often worsen due to reduced activity, stress on organs and infection risk.

Preventive Strategies for Winter Health

Maintain Body Warmth

Layered clothing and warm environments reduce cold stress.

Support Immunity

Adequate nutrition, vitamin intake and sleep strengthen immune defences.

Stay Physically Active

Indoor exercises and regular movement prevent stiffness and metabolic decline.

Manage Chronic Conditions

Regular monitoring and medication adherence are critical during winter.

Hydration and Skin Care

Drinking fluids and using moisturisers prevent dehydration and skin damage.

Role of Preventive Healthcare

Preventive healthcare helps:

identify seasonal risk factors
adjust treatment plans
prevent winter complications

NITI Aayog highlights seasonal preparedness as an important public health strategy.

When to Seek Medical Help

Medical attention is necessary if:

infections persist or worsen
chest pain or breathlessness occurs
joint pain limits mobility
mental health symptoms interfere with daily life

Early care prevents serious outcomes.

Long-Term Impact of Ignoring Winter Health Risks

Ignoring cold weather effects may lead to:

severe infections
cardiovascular events
chronic pain progression
reduced quality of life

Seasonal awareness plays a critical role in long-term health.

Conclusion

Understanding how cold weather affects health allows individuals to take timely preventive measures. Winter increases the risk of infections, heart strain, respiratory problems, joint pain and mental health challenges. With proper warmth, nutrition, activity and preventive healthcare, most cold-related health issues are manageable and preventable. Seasonal care is not optional—it is essential for protecting health and wellbeing throughout the colder months.

References

ICMR – Seasonal Health and Infectious Disease Reports
National Family Health Survey (NFHS-5) – Seasonal Morbidity Data
NITI Aayog – Preventive Healthcare and Seasonal Preparedness Strategy
WHO – Cold Weather and Health Impact Guideline
Lancet – Seasonal Variation in Cardiovascular and Respiratory Diseases
Statista – Winter Health Trends and Illness Data
Indian Journal of Public Health – Climate and Health Studies

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