With the COVID-19 pandemic still sweeping the world, it’s easy to forget about the annoying, yet far more benign viral infections that plagued us thus far.

The flu and the common cold are some of the most common respiratory infections. Both are caused by highly infectious viruses, although from different families of viruses.

The common cold is caused by over 200 different viruses. About 30-35% of all adult colds are caused by rhinoviruses, but some cases are also caused by a handful of coronaviruses, the older cousins of the virus that causes COVID-19. This huge diversity of viruses is one of the reasons why we don’t yet have a universal vaccine for the common cold.

Meanwhile, the flu is caused by only a couple of influenza viruses, enabling researchers to develop new vaccines every year to neutralize new mutations and keep seasonal outbreaks at bay.

How long are you contagious with the flu?

The typical incubation period for influenza is one to four days, meaning it takes about that much time for symptoms to show after the initial infection. However, people can pass on the illness to others a day before the onset of symptoms and up to seven days after symptoms first show. The most infectious period is 3 to 4 days after you start feeling sick.

Children and adults with poor immune systems may be infectious for a few days longer.

Like most respiratory viruses, influenza is spread through direct contact, from one person to another. This can happen when an infected person sneezes or coughs into the air and then a susceptible host comes in contact with these viral-loaded droplets of moisture.

In order to protect co-workers and school colleagues, Dr. William C. Wilson, who is the chief medical officer of the University of California Irvine Health, recommends you make sure you check all item on this list to be on the safe side:

• No fever for 24 hours — without fever-reducing medications
• No vomiting or diarrhea for at least 24 hours
• Coughing or sneezing should be reduced and intermittent

How long are you contagious with the common cold?

People sick with the common cold will be contagious for much longer than is the case for the flu. While people sick with the flu will generally stop being contagious after a week, those sick with the common cold may be contagious for up to three weeks.

It depends a lot on the kind of virus involved. If the common cold symptoms are caused by a rotavirus, you can spread it to others even before you develop symptoms — and up to two weeks after you’ve recovered.

Generally speaking, you’ll be contagious 1-2 days before the onset of symptoms and for up to 2 weeks. You’re more likely to infect others during the first few days, when symptoms are at their worst.

After common cold symptoms fade away, you should still wait 24-36 hours before returning to your normal work or work schedule.

How do I know if I have the cold or the flu?

Many symptoms for both types of viral infections overlap, such as cough, runny nose, and feeling tired, which can make it challenging to tell the difference between the two.

Colds come on gradually over a few days and are often milder than the flu. They usually get better in 7 to 10 days, although symptoms can last for up to 2 weeks.

Flu symptoms come on quickly — often within 1 to 3 days — and can be severe. Basically, if you wake up one morning suddenly feeling like you’ve been hit by a truck, it’s likely the flu. Symptoms usually last 1 to 2 weeks.

Influenza is responsible for head and body aches, whereas cold aches are much milder.

With a cold, you may or may not feel tired. With the flu, however, tiredness and weakness are common.

Some people get a slight fever when struck by a cold, but most don’t. In contrast, any fever above 38 degrees Celsius (101 to 104 degrees Fahrenheit) is a sign of the flu, with children’s fevers tending to be higher.

Tips for returning to work after being ill with the flu or common cold

If you’ve gained at least 90% of your energy back and overall symptoms are gone or decreased significantly, it may be safe to return to work or engage in social activities. When you do return, remember:

• Wash your hands frequently and sanitize any surfaces such as computer keyboards and telephone handsets and receivers.
• Protect your coworkers by avoiding those with weakened immune systems.
• If you are still coughing or sneezing, wear a medical mask to prevent the spread of virus-filled droplets.
• Sneeze or cough into a tissue or into the bend of your elbow — not your hand — to keep droplets from spreading.
• Ease back into your work pace to allow your body to recover fully and to prevent yourself from relapsing back into illness.