How do I know if I have Covid? Only a test can say for sure

As the country experiences another surge of Covid cases this summer, medical professionals are emphasizing that it is extremely difficult to determine if someone has the virus solely based on their symptoms.

Dr. Steven Furr, a family doctor in Jackson, Alabama, and president of the American Academy of Family Physicians, mentioned that every week they come across surprises regarding Covid testing results. Some people who seem healthy end up testing positive, while others with symptoms test negative.

"It's extremely difficult to distinguish Covid from any other respiratory illness at the moment," he remarked.

Patients with Covid are coming in to clinics with a variety of symptoms, according to Furr and other doctors.

Dr. Paul Sax, who oversees the infectious diseases department at Brigham and Women's Hospital and teaches medicine at Harvard Medical School, explained that some individuals experience traditional symptoms like a sore throat, runny nose, cough, and slight fever when infected. However, others may primarily have nausea and diarrhea with only minor respiratory issues. The range of symptoms can be quite wide and diverse, varying from one person to another.

Dr. Bernard Camins, the head of infection prevention at the Mount Sinai Health System in New York City, has observed a similar pattern.

According to Camins, without a test, it is difficult to determine whether you are dealing with a common cold or Covid.

By the middle of June, the Centers for Disease Control and Prevention reported that Covid cases were increasing in 39 states. The number of emergency room visits, hospitalizations, and deaths related to Covid have also risen.

Covid Mutates For Higher Contagiousness

The way we diagnose illnesses has changed significantly since 2020, when a high temperature was seen as a major sign of Covid.

Furr mentioned that a single symptom is no longer a definitive indicator of Covid. Without a test, it is impossible to accurately determine if someone is infected with the virus.

There are several factors contributing to the shift. Almost everyone's immune system has encountered the virus on numerous occasions from either being vaccinated, getting infected, or both.

"That seems to improve the seriousness of the illness as time goes on," Sax explained. "Repeat infections are usually less severe than initial infections - not all the time, but most of the time."

Additionally, the virus has continuously mutated over time. The most recent omicron subvariants, including KP.3, KP.2, and LB.1, are good at causing illness in individuals but typically not severe illnesses.

LB.1 stands out as a variant that might spread more easily among people due to a specific change in a spike protein, according to a representative from the CDC. Nevertheless, there is no proof at the moment that LB.1 leads to more serious illness.

At the beginning of the month, the Food and Drug Administration instructed vaccine manufacturers to focus on the KP.2 strain for the upcoming round of Covid vaccinations this fall. Tomorrow, a panel of advisors from the CDC will meet to talk about who should receive these shots.

The specialists are least likely to suggest that older adults aged 65 and above and individuals who are severely immunocompromised, like organ transplant recipients, should receive updated Covid vaccines to reduce the risk of complications.

Individuals with preexisting conditions are also probable to be included. Sax mentioned that a significant number of individuals who are currently hospitalized due to Covid-19 are also dealing with other long-term health issues, such as congestive heart failure.

He started by mentioning that their heart is not functioning properly. And when Covid arrives, their congestive heart failure worsens.

Timing Of Testing & Isolation?

With the variety of potential Covid symptoms, it can be challenging to determine when a test is necessary. Additionally, tests could provide incorrect results if taken too soon.

Dr. Abraar Karan, who specializes in infectious diseases at Stanford Medicine in California, mentioned that some patients initially test negative but then test positive a day or two later. This is expected, as the level of the virus in the sample needs to reach a certain threshold in order for it to be detected.

Antigen tests, which many Americans have stored at home, are particularly prone to giving incorrect results when people start to feel sick.

According to Sax, rapid tests may not show a positive result during the initial onset of symptoms. It typically takes two to four days for the test to detect enough of the virus to confirm a positive result.

If someone tests positive, they no longer have to stay isolated for five days, according to the CDC's latest advice.

Instead, the CDC recommends that individuals remain at home if they are showing symptoms, but can resume attending school, work, and social events once they have recovered.

Sax mentioned that there are no strict guidelines about when to stop isolating once the symptoms have improved or are almost gone.

Erika Edwards writes about health and medical news for NBC News and "TODAY." She is a reporter for these outlets.