Flu, Covid and bronchiolitis: how to tell them apart and how to treat them

Influenza: definition, symptoms and treatments

Influenza or flu is a contagious respiratory illness transmitted by an influenza virus. Usually mild, its symptoms include a high fever above 38.5 °C, dry cough, headache, aching muscles and intense fatigue (1-2).

In more vulnerable groups, however, such as new-born babies, those over 65 or immune-compromised individuals, it can cause serious complications (lung failure, exacerbation of chronic bronchitis, decompensation of asthma) (3).

The incubation period for flu is between 1 and 3 days. A person is contagious from the day before symptoms appear and may continue to be for up to a week. The virus is transmitted via airborne droplets (saliva and nasal secretions in coughs and sneezes) and also indirectly through touching contaminated surfaces (4).

Flu epidemics normally start in winter due to three conjunctive factors: we spend more time indoors in close proximity to others, our nasal mucous membranes become drier making it easier for the virus to invade, and the flu virus may survive better in the cold (5).

As most people recover by themselves, treatments are aimed at easing symptoms only - staying well-hydrated and taking painkillers and medication to reduce the fever and cough. Antivirals may be prescribed for more vulnerable individuals to prevent progression to more serious illness (6).

Covid-19: how it differs from the flu

First appearing in December 2019 in China’s Wuhan province, Covid-19 (which stands for COronaVIrus Disease 2019) is a viral respiratory infection transmitted by the SARS-CoV-2 coronavirus (7).

A feature of the Covid-19 virus is the wide variety of symptoms it produces (8). While some people remain asymptomatic, others display classic symptoms of a respiratory infection, such as fever or cough, combined perhaps with muscle pain, headache, sore throat or nasal congestion. In such cases, it’s particularly hard to distinguish it from the flu.

However, there are certain characteristics which are much more suggestive of a Covid infection, such as loss of taste (ageusia) or smell (anosmia) (9). Digestion-related problems (nausea, vomiting, diarrhea…) or skin issues (redness, rashes, chilblain-like symptoms…) have also been reported (10).

In more severe forms, which usually develop in the second week of infection, pulmonary tract symptoms may be associated with hyperinflammatory syndrome, causing shortness of breath (dyspnoea) and oxygen desaturation, which require the patient to be hospitalised (11).

Covid-19 also has a longer incubation period than flu (5-8 days) and a contagion period which starts 2-3 days before the first symptoms appear (12). Transmission gradually decreases until the 7^th day of symptoms, but in exceptional cases, may continue until the 14^th day.

It is transmitted in the same way as flu, namely by airborne droplets spread by coughing or sneezing, or by contact with contaminated surfaces. Hence the introduction of barrier measures (face masks, social distancing, washing hands with alcohol-based sanitizers…)

For mild to moderate forms, there is no recommended treatment, though paracetamol can be taken in order to bring down the temperature. However, non-steroidal anti-inflammatories or NSAIDs (such as Ibuprofen) are not recommended as they can reduce the body’s immune response. As of February 2022, doctors have been able to prescribe an anti-viral treatment (Paxlovid®) to those at higher risk of complications (13).

Bronchiolitis: the common infant infection

Bronchiolitis is a viral respiratory illness affecting the bronchioles (small bronchi). It is generally caused by an RSV (respiratory syncytial virus) (14).

Usually mild, it primarily affects babies and children under 2 during the winter period. It normally starts with a simple cold and mild cough. The coughing fits get worse over a few days before gradually improving. They may be accompanied by wheezing or difficulty breathing, and even fever. The child sometimes finds it hard to sleep or eat(15).

The virus can also affect older children and adults but without causing any symptoms, or at worst, a slight cold. However, it is still highly contagious and spreads silently among the population. It is easily transmitted by saliva, coughing and sneezing, and also remains on hands and objects (dummies, security blankets, toys…).

If you’re a parent of a baby or young child, there are specific steps you can take to prevent the spread of bronchiolitis (16):

• wash your hands for 30 seconds after touching your child;
• wash toys and stuffed animals regularly;
• ventilate your child’s room for 10 minutes a day;
• wear a mask, especially if you have a cold yourself;
• avoid confined or public places, especially if your baby is less than 3 months old;
• don’t share unwashed baby’s bottles, dummies or cutlery;
• don’t smoke in front of your child.

Fortunately, babies and childrennormally recover by themselves within 5-10 days though the cough may persist for 2-4 weeks. Treatment essentially consists of regularly clearing the nasal passages and feeding smaller amounts more frequently.

Hospitalisation is not usually necessary, except in the case of worsening symptoms in babies either aged less than 6 months, born prematurely or suffering from respiratory or heart disease.

A few tips for preventing illness and supporting your immune system

You can help avoid and stop the spread of winter viruses by adopting the following good habits:

• wash your hands regularlywith soap and water or by rubbing them with an alcohol hand sanitiser (17);
• wear a mask in confined, poorly-ventilated places (such as public transport) especially if you have symptoms (18);
• air your living spaces every day (19);
• eat a diet rich in vitamins et minerals: fresh fruits and vegetables for their vitamin C content, oily fish for vitamin D… (20-21);
• make sure you get enough sleep, preferably 7-9 hours a night (22).