"I was feeling lethargic, my throat was hurting, definitely it was phlegymy. I totally thought it was the flu because everybody was talking about the flu," he said.
But according to doctors, self-diagnosis can backfire, and things got worse for Rosenberg.
"My throat was killing me and it was itching, and then I had this pounding pain in my head," he said.
Ear, nose and throat specialist Dr. Michael Bublik says Rosenberg's story is typical of many patients who search the Internet for diagnostic information and treatment.
"He had muscle aches, the usual kind of symptoms you would have with the flu. But he had a sore throat as well. He read up online, decided to come in, took no medications," said Bublik. "I examined him, took a look in his throat, he ended up having strep throat."
When you type in flu symptoms into Google search, about 74 million results come up. Doctors say some of it is reputable, but a lot of it is misinformation or ads for drugs you don't need, and some of it can scare you away from taking the proper action.
"There's definitely a danger to it," Bublik said. "They go on these blogs and there are these horror stories. You kind of have to take what you read with a grain of salt," said Bublik.
Bublik also said it helps when patients are educated, but he advises sticking with websites from reliable sources.
"Usually the big university clinics have good web sites. Those are the ones you kind of want to stay with," he said.
Experts agree most cases of the flu can be treated at home with rest and fluids.
"But if you have unusual symptoms like severe, severe sore throat, severe sinus headaches, severe drainage from your nose, severe allergies, those things can be different from the flu," said Bublik.
Rosenberg suffered a lot longer than he should have, and next time he knows.
"It's better to be safe than sorry," he said. "I will definitely come see a doctor a lot faster the next time."
If you have an infant, have underlying medical condition or you're elderly, Bublik says you definitely want to check with your doctor if you think you have the flu. Also, if you don't seem to get better after four to five days, it's another reason to call your doctor.