Immune and infectious diseases Archive

Many COVID-19 symptoms — such as fever, cough, or muscle aches — overlap with the symptoms of other respiratory conditions, such as influenza, a common cold, or asthma. But there are differences among the conditions. For example, a bout of the flu or a cold will not cause shortness of breath the way COVID-19 will. And while asthma can cause shortness of breath, it won't cause a fever or body aches the way COVID-19 will. A person who's experiencing concerning symptoms of respiratory illness should report them to a doctor.

Hives are red, itchy welts that crop up on the skin. Allergic reactions and stress, among other triggers, can cause episodes of hives, which typically last several days to a couple of weeks. Cases that last six weeks or longer may be autoimmune hives.

COVID-19 can damage the brain in many ways. Initially, it can cause brain inflammation that causes confusion, difficulty concentrating, and memory problems. COVID also can cause new psychological disorders such as depression or anxiety. It can even cause people to see and hear things that aren't there and to believe things that aren't true. COVID often damages the brain's autonomic nervous system, leading to abnormalities in heart rate and blood pressure. Additionally, the virus that causes COVID can infect and injure the lining of blood vessels and make blood clot more easily, which can lead to strokes and heart attacks.

People who have had shingles have a 30% increased risk for heart disease and stroke, says a new Harvard study. Learn more about the risk.

Getting at least one dose of a COVID vaccine lowers the risk of developing long COVID even among people who were previously unvaccinated and recovered from COVID.

A 2022 observational study that included more than 200,000 people found that those who'd had shingles at some point had a 30% higher long-term risk for a major cardiovascular event, compared with people who didn't have shingles.

A fever is the immune system's response to an infection or invader. Most fevers drop after people take over-the-counter medications. People should call a doctor if their fever reaches 103° F and go to an emergency room if it reaches 105°.

Wintertime can pose challenges to cardiovascular health. Cold temperatures can cause arteries to narrow, which can leave people with heart disease vulnerable to angina or heart attacks, especially during physical exertion. Changes in sleep, eating, and exercise habits related to the season may also affect the heart. Crowded indoor gatherings also raise a person's risk for respiratory infections, which can exacerbate heart disease.

Another holiday season is here, and this year we need to contend with other viruses besides COVID-19. Three Harvard experts share their thoughts on the best ways to keep ourselves and our family members healthy as we celebrate holidays together.

Everyone experiences acute (short-term) diarrhea at some time. The unpleasant experience often resolves on its own in a few days, but there are situations that require medical attention. Examples include bloody diarrhea, severe abdominal pain, a high fever, and episodes that continue for a week or longer. A medical consultation can help determine if diarrhea is related to a specific bacterium or parasite, a medication side effect, a food intolerance, or an inflammatory bowel disease.