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"There are some patients that we’ve been following for a year or a year and a half that have not recovered. And that’s where we need more research on therapeutic options for them,” said Dr. Luis Ostrosky, chief of infectious diseases at UTHealth Houston and Memorial Hermann Hospital. (Getty Images)

As Americans gather indoors in the late fall and winter months, experts are urging caution, with cases of Covid-19 already on the rise.

Even though most people in the U.S. have been exposed to COVID-19, there is still a risk of long COVID.

What is long COVID?

There is no agreed upon method for defining long COVID.

According to the Centers for Disease Control and Prevention, more than one in five Americans who had COVID-19 still have symptoms of long COVID, which the CDC defines as symptoms lasting more than three months post-infection. The CDC says that while long COVID is more common in people who have had a severe bout of COVID, even people who have not had a severe bout can have long COVID symptoms.

There are three types of patients that the chief of infectious diseases at UTHealth Houston sees at the hospital's long COVID clinic.

The good news is that most of the last category of patients will improve on their own within four to six months.

Some patients that we have been following for a long time have not recovered. There is more research that needs to be done on therapeutic options for them.

What happens if you already have long COVID and get infected with COVID-19 again?

It can be a big blow if you get another infection.

Ostrosky said that he has seen patients with long COVID who have been re-instated with the disease. The four- to six-month recovery process may have made a lot of progress for them. It's very sad for them when this happens.

There is still more research to be done on how reinfection affects people with long COVID. 80% of those who described themselves as still having long COVID symptoms reported that another case of COVID-19 made their symptoms worse.

40% of those who were in recovery or remission from long COVID said that the second bout was just as bad as the first one, 32% said it was less severe and 28% said it was more severe.

Dr. Jessica Justman, an associate professor of epidemiology at Columbia University, was not involved in the survey. If you've had long COVID, getting an infection again could make you feel like it's getting worse. It is an additional reason to get a vaccine.

If you haven’t had long COVID before, how might a second (or third or fourth) COVID-19 infection affect your chances of developing it?

A recent study using data from the Department of Veterans Affairs’ national health care database found that reinfection increased the risk of long COVID as well as other adverse health outcomes. (Getty Images)

According to the CDC, symptoms from reinfection are likely to be less severe than the first infection, but that some people can experience more severe COVID-19 during reinfection, and that the assortment of variant may mean that an individual may not have as much immunity from a previous infection as is

Even if you don't get long COVID the first time, it's possible to get it if you get re-instated with the virus.

Future performance is not predicted by past performance. If you have had a mild case before, you don't know if the next one will be as mild or more severe.

There is a lot of infections that we don't know about. Don't let your guard down

A study published last week found that reinfection increased the risk of long COVID, as well as other adverse health outcomes, including a twofold increased risk of death and a threefold increased risk of hospitalization.

Senior author Ziyad Al-Aly said that the research showed that getting an infection a second, third or fourth time contributes to additional health risks.

The study found that if participants were unvaccinated, they were at increased risk of re-infection. The impact of vaccine status on long COVID outcomes is still unclear. The authors found that people who received the vaccine were less likely to develop long COVID than people who weren'tvaccinated. Some studies show that people who receive two doses of the vaccine are less likely to develop long COVID.

The study shows us that there is still a lot to learn about the long-term consequences of multiple episodes.

The retrospective nature of the study means that some outcomes could have been missed. The study could not follow participants in real time because the data was collected retroactively. According to Justman, if the cases had been properly counted, the risks of re-infection might have been reduced.

The dose-response relationship was seen by them. People with two infections had a higher risk of dying than people who had just one. When you see that kind of relationship, you know what you are looking at.

What happens next?

"It’s still important to take advantage of all the vaccines that you can possibly avail of, i.e. flu vaccine, COVID boosters. And if you’re in a crowded indoor place, think very carefully about your COVID exposure, and try to see if you can wear a mask if at all possible," Dr. Jessica Justman, an associate professor of epidemiology at Columbia University said. (Getty Images)

There are a number of studies underway that could provide answers to some questions. In order to learn more about the long-term effects of COVID-19, the National Institute of Health is conducting a study. The CDC is conducting a number of studies with partners, including with Nova Southeastern University for a project called "COVID-19: Understanding the Post-Viral Phase (COVID-UPP)," on patients who continue to have symptoms more than three months after an infectious disease.

There will be a lot of information coming out, so it is kind of a 'watch this space'. It's definitely a work in progress, but I think what we've learned so far would reinforce those same messages that everyone in public health keeps repeating over and over. It is important to take advantage of all the vaccines you can get yourself. Try to see if you can wear a mask if at all possible if you are in a crowded place.