Before the Covid-19 pandemic, parents of schoolchildren approached winter expecting they’d have to grapple with seasonal ailments: the common cold or the flu, their arrival announced by stuffy noses, sore throats, coughs and low-grade fevers. Inconvenient for child and parent, but not usually serious.

This year, those same symptoms could be a more ominous signal. What should parents do not knowing whether a fever is just a cold or flu, or an indicator of Covid-19? Should they test their child? If so, when? And even if their children test negative, how long should parents and their children isolate before returning to work or to school?

“Inevitably, kids go to school all the time when they're sick. That's what makes this so tough,” says Annette Anderson, deputy director of the Johns Hopkins University Center for Safe and Healthy Schools says. "Your kid could be coughing and sneezing and sitting next to my kid (in class), and your kid could have Covid.”

It’s not easy to distinguish between common Covid-19 symptoms like a cough or a fever with symptoms of the common cold or flu. Illness in children with Covid-19 is more serious and can include diarrhea or congestion as well as the loss of taste or smell, fatigue, headache and sore throat. What should parents do if a child has one or more of those symptoms? Keep them home.

“The likelihood that every sick person has Covid is low,” says Yvonne Maldonado , a professor at the Stanford University School of Medicine and chair of the infectious disease committee for the American Academy of Pediatrics (AAP). “But you just don't want to take that risk. Even if they don’t have Covid, you don’t want to be spreading that around in school.”

Nearly 490,000 children under 18 in the United States have tested positive for SARS-CoV-2, the virus that causes Covid-19, according to the Centers for Disease Control. An earlier CDC study of schoolchildren issued in September found that 63 percent of cases were in children aged 12 to 17 while 37 percent were in those aged 5 to 11. Children rarely die from the virus so public health officials have mostly focused their concern on whether they can be infected at school and then transmit it at home. About 3.3 million adults older than 65 , those most vulnerable to the virus, live with a school-age child.

Even if a child probably just has a cold, the mere possibility that they could transmit Covid at school to another child who lives with their grandparents presents a dilemma at the core of public health recommendations.

According to Margaret Fisher , a pediatric infectious disease researcher and professor at the Drexel University College of Medicine, the incidence of the virus within a community is important context for testing. For instance, if a child suffers from hay fever every fall, has not been exposed to someone with the virus, and is in an area where there's not an outbreak, then Fisher says there may not be a reason to have them checked. “On the other hand if you're in an area where there are now 500 new cases a day and your child has symptoms which might be allergies, but could be Covid, then you're going to test them for the virus,” she says.

Why not just quarantine a child suspected of being infected? Getting a child tested is important not only for contract tracing, but also to create an accurate picture of disease transmission in an area to guide schools on reopening. While millions of kids are back in school at least part-time, many large districts remain closed, a sign for parents, teachers and administrators to be vigilant.

New York City schools, one of the few large systems opening, are keeping an eye on the spread of Covid-19 with a monitoring program that tests 10 to 20 percent of staff. Across the country, the Los Angeles public school system has a $150 million program testing students even before classrooms open to brick-and-mortar instruction. Testing is expected to eventually take place at 42 sites, though key details, including how often staff and students will be tested, are still in the works. The district announced earlier this month that continuing high infection rates means early testing of staff.

But over a vast swath of the country between those giant school systems, extensive testing for 56 million students is too expensive and too logistically difficult to administer now—though cheaper, rapid tests are on the way. The largest school districts in Texas— Houston, Dallas, Austin, and El Paso—are not comprehensively testing students and teachers. Minnesota is only testing school employees. Boston is testing a rotating five percent of teachers weekly.

The American Academy of Pediatrics’ guidelines , as well as those from the CDC, Maldonado says, do not recommend universal testing of students. Tests are only a snapshot in time, cautions Fisher. Children can be infected for days and shedding virus before a test returns positive. "This is where it gets tricky," Fisher says, "You have to be very careful about the timing of your testing and people have to understand what a negative test means. It does not mean you're not infected."

That’s why protective measures, like wearing masks, distancing and washing hands, are key. They slow the spread of not only Covid-19, but the cold and the flu. “The devil is in the details,” says Maldonado. Rooms need to be set up properly and distancing enforced. Children older than 2 need to wear masks. The pediatric academy guidelines call for encouraging alternate transportation to schools and limited capacity on buses when used. They suggest having one-way hallways, having teachers rotate into classrooms and minimizing the number of students in a cafeteria at a time. "It's not going to be easy," she adds

Anderson, though, worries that relying on parents to keep their child home with a runny nose or cough when the adults need to work, represents a blind spot on behalf of officials on school reopening plans.

“We've perhaps put our children in danger because we don't have transparency, policies and consistency among districts to know what best practices look like," she says. "We're building the plane while we're flying it."

Parents, she says, should continue to advocate for their children and be part of a conversation about school policies. By weighing in on how cases are tracked or how schools reopen, parents can then make their own decisions about whether to have their children learn at home, take part in a hybrid situation or go to school. “Parents are going to have to be at the table and be part of these conversations,” says Anderson. “Parents are in the driver’s seat now and I think that parents will continue to be in the driver’s seat moving forward.”

Fisher says parents can also do a little educating of their own to help children who want to see their friends and get back to something resembling normal by reminding them of the basics of infection protection.

“They (children) need to understand that we don’t know who is shedding the virus at any time,” she says. “So to protect themselves and their families they need to be wearing a face covering and they should physically distance.”