The winter surge of flu-like illnesses and a variety of contagious infections continue to grow. But how do you know what you have? It can be tricky to figure out, that's why doctors say it's important to know what you have so you can get the right kind of treatment.

"It can be very difficult to differentiate one from another," Dr. Martin Topiel, an infectious disease physician at Virtua Health, said.

Topiel said tests can be helpful, but symptoms, which can be similar, are the best clues.

"So all these viruses are a little different in how they transmit. The bottom line is we have to be careful at all times right now during this dangerous winter season," Topiel said.

Influenza

The flu usually has a very fast onset, with people feeling like they've been hit by a bus.

The main symptoms are fever, headache, body aches and fatigue. 

"We expect people to be sick anywhere from 48 hours to five days," Topiel said.

If taken quickly, Tamiflu can reduce the severity and duration of the flu. Otherwise, people are advised to rest, stay hydrated and take over the counter medications to relieve symptoms.

The common cold

Colds are spreading fast, too, and develop more slowly. The main symptoms are congestion, sneezing and sore throat.

Colds aren't bacterial infections, so antibiotics usually aren't prescribed unless a sinus or ear infection develops.

RSV

Respiratory syncytial virus, or RSV, is also spreading mostly among young children.

The main symptoms are wheezing, difficult breathing and fever. Best treatments include fluids, acetaminophen.

COVID

The spread of COVID has been minimal. Symptoms include breathing difficulties, fatigue and loss of taste.

"With COVID, of course, it could last a longer time period," Topiel said.

Doctors said the best prevention is vaccines, except for a cold, there isn't one. Good hand washing also helps prevent the spread of infections.

Doctors said it's important to get medical care if a high fever persists and there's difficulty breathing. A humidifier can also be helpful in limiting the spread of virus particles.