If you’ve felt like you had Covid recently but tested negative, you’re not alone.
A wave of respiratory and stomach bugs have been sweeping the US for months, striking earlier and more severe than usual and causing similar symptoms to the pandemic virus.
Norovirus is a very contagious stomach bug that causes vomiting and diarrhea. Like Covid it can cause headaches, chills and a fever.
But there are some ways to tell between the two.
For norovirus, symptoms usually start one or two days after being infected and . Dehydration is often the earliest warning sign. A dry mouth and throat, listlessness, dizziness and increased urine output could also occur if the patient is dehydrated
The above graph shows norovirus cases by year, with this year’s data 2022/23 shown in red. Last year’s (2021/22) is the blue dashed line, while the previous year is the blue dotted line. The average for the period before the pandemic is shown in gray. It reveals that cases of norovirus are pointing sharply upwards in the 14 states where they are monitored
The telltale symptoms of norovirus, often known as the summer flu or travelers’ diarrhea, are nausea, vomiting and diarrhea.
Some people also have a high temperature, a headache and aching arms and legs.
Symptoms usually start one or two days after being infected. Dehydration is often the earliest warning sign.
A dry mouth and throat, listlessness, dizziness and increased urine output could also occur if the patient is dehydrated.
There are a lot of overlapping symptoms between the two, but Covid has more upper respiratory symptoms, a cough and the hallmark loss of taste or smell.
Even though anosmia has become less common with new Covid variants, it rarely appears at all in other viral illnesses.
Other Covid symptoms include fatigue, shortness of breath and a dry cough.
Another key difference between the two is that Covid symptoms usually last for two weeks whereas norovirus sufferers typically recover in a couple of days.
People with either can usually manage their symptoms at home by drinking a lot of fluids to avoid dehydration.
In more serious cases, norovirus can lead to dehydration and even death.
Official data shows norovirus infections are up 66 percent in 2023 compared to last year and are rising across the country.
Experts say the virus is took off earlier than normal, erupting around New Year’s instead of its usual rise in late-February.
Google searches for norovirus have risen more than six-fold since the start of February, a signal that more Americans are suffering these symptoms.
Official data from the Centers for Disease Control and Prevention (CDC) shows that 225 norovirus outbreaks have been recorded since August, already up a third on the 172 recorded in the previous year.
The CDC does not routinely test for, track and report norovirus information like it did for Covid, meaning actual case numbers are likely much higher.
In the most recent update – including data for the week ending January 9 2023 – more than 20 outbreaks were recorded.
For comparison, during the same week last year, there were 15 outbreaks. Cases are rising in all 14 states that report data to the CDC.
These states include Alabama, Massachusetts, Michigan, Minnesota, Nebraska, New Mexico, North Carolina, Ohio, Oregon, South Carolina, Tennessee, Virginia, Wisconsin and Wyoming.
There are also concerns the illness could be more serious than usual after lockdowns robbed children of vital immunity for fighting viruses.
Norovirus is usually acquired by eating contaminated food, or touching a contaminated object and then putting your hand in your mouth.
But, it can also spread from person-to-person through close contact with someone who is infected.
Dr Simon Clarke, an Associate Professor in Cellular Microbiology at the University of Reading told our sister publication MailOnline: ‘Good hand hygiene and not putting your fingers in your mouth are really important to reduce chances getting norovirus’.
He added: ‘Nobody knows whether the last person to touch a door handle or lift a petrol pump, unwittingly deposited something unpleasant which could make you sick.’
Medics say the best way to avoid infection is to wash hands regularly, adding that hand sanitizers — which worked against Covid — do not work against norovirus.
Experts also say hand sanitizer does not destroy the virus because it is resistant to alcohol.
This means only thorough hand washing can help someone avoid catching it.
Norovirus can spread all year round, but cases tend to rise in the late winter driven by more social events spurred by the warming temperatures.
The virus is passed on via fecal matter that gets onto the hands and then transferred to other surfaces people touch. Ingesting only a small amount of the virus can trigger an infection.
Patients tend to suffer a mild illness lasting for about one to three days, suffering symptoms including nausea, vomiting and stomach pain or cramps.
Those most at risk of catching norovirus include young children yet to have built up immunity against it, those with underlying conditions and the elderly.
There are no vaccines available, with medics saying it is best to allow the infection to run its course.
A CDC spokeswoman previously told TODAY: ‘While norovirus cases are rising in the US, CDC data as recent as January 2023 shows that reported norovirus outbreaks are within the expected range for this time of year.’
Norovirus causes 19 to 21 million cases of vomiting and diarrhea, 109,000 hospitalizations and 900 deaths.