An Overview of Astrovirus

Astroviruses are a type of virus that causes diarrheal illness (gastroenteritis). Infants and young children are most likely to have diarrhea caused by astroviruses, but the infection also occurs in the eldery and those with compromised immune systems.

Although it can cause symptoms similar to other common viral infections, diarrheal illness from an astrovirus infection is generally much less severe than those caused by rotavirus and norovirus. It also rarely requires any medical treatment. However, researchers are still learning about human astroviruses. Our knowledge of how they work is still new compared to other viruses that cause similar illness.

Astroviruses are one of several pathogens that can cause gastroenteritis in humans. The main symptom caused by astrovirus is diarrhea. Compared to other microorganisms that can cause gastroenteritis, such as rotavirus and norovirus, diarrhea caused by astrovirus is usually mild.

While mild diarrhea is the main symptom astroviruses cause, a person who gets sick may also have other common symptoms of gastroenteritis, including:

• nausea
• vomiting
• stomachache
• no appetite
• body aches
• fever

The symptoms of gastrointestinal illness caused by astroviruses usually resolve on their own.

Babies, very young children, the elderly, and people with compromised immune systems (such as those being treated for cancer or HIV/AIDS) are more likely to become dehydrated.

Otherwise healthy people generally recover from a mild illness caused by astrovirus in a few days. In some cases, they may not even know they have been infected by an astrovirus because they do not feel sick (they are asymptomatic). A person who is infected but not showing symptoms (referred to as a "carrier") is still able to spread the virus to others.

Astroviruses got their name because they have a star-like appearance when viewed under a microscope. There are several different kinds of astrovirus, some of which infect humans. The virus has also been found in other animals including dogs, birds, pigs, cows, bats, and even dolphins.

Infants and young children (under two years of age) are most likely to have a diarrheal illness caused by astroviruses. While it's less common than other infectious pathogens that cause diarrhea (such as rotavirus) astroviruses account for 2 to 9 percent of viral gastroenteritis cases in children around the world.

The infectious virus particles are very tiny and it only takes a few of them to make a person sick.

Someone who is sick can spread the infection to others. Even after a person starts to feel better, they may still be shedding virus particles in their stool, meaning they can still make others sick.

Astrovirus can be transmitted between people in a number of ways, but a person's risk for infecting others is increased by certain factors.

Astroviruses tend to circulate more frequently during particular seasons, depending on the geographic region. In parts of the world with a temperate climate, illnesses associated with astroviruses seem more frequent in the winter and spring. In tropical climates, it's more common during the rainy season.

However, astroviruses are present year-round and can make people sick at any time, especially in places where sanitation is poor or people live in crowded spaces.

Illness caused by astroviruses is generally mild and does not require medical attention. While anyone can get sick from the virus, most cases occur in children under the age of two. Most children have developed antibodies to astroviruses by the time they reach around 10 years old. This protection is why astroviruses do not usually make adults sick.

However, it is believed that immunity wanes over time, which is why elderly people are more likely to get sick from the virus.

Additionally, any person who has a compromised immune system from other illnesses (such as HIV/AIDS), or because they are undergoing medical treatments that affect the immune system (like chemotherapy for cancer) are also more susceptible to viral illnesses.

When a person who is sick seeks medical care, a health care provider will consider their symptoms, the results of an exam, and whether they have been around other sick people recently.

In other cases, a doctor may order additional tests to determine which virus has caused a person's illness, especially if several people who have something in common (such as eating the same food or attending the same daycare) get sick around the same time.

Tests that a health care provider might order to help identify the virus include:

• stool culture to see if the virus is present.
• blood tests to look for antibodies to the virus.
• special tests called assays, such as reverse transcription-polymerase chain reaction (RT-PCR) to determine which astrovirus is causing the illness.

Viral gastroenteritis can be caused by several pathogens. While it's not common, it is possible for a person to be infected by more than one at the same time (called coinfection). An outbreak may occur if there are many people who are ill at the same time or seemingly due to the same source of infection. However, unless an outbreak is suspected, it is usually not necessary to identify the exact virus.

An illness that is caused by a virus cannot be treated with antibiotics. Therefore, if any treatment is prescribed for viral gastroenteritis caused by an astrovirus, it is typically only used to address symptoms (such as nausea) and to provide supportive interventions (such as fluid replacement for dehydration).

While there is no specific treatment for astrovirus infections, no cure, and no vaccine, there are steps that people can take to help protect themselves and others. Steps people can take to help prevent the spread of viral infections, including astrovirus, include:

• proper handwashing, especially after using the bathroom.
• not sharing eating utensils or drinking cups.
• staying home from work or school if you are sick.
• avoiding the handling and preparation of food during and when recovering from illness.
• carefully following directions when using antiseptic or disinfectants on surfaces.

Researchers are still learning about astroviruses in humans and are continuing to explore possibilities for treating the infections they cause.

A Word From Verywell

Astroviruses are one of several viruses known to cause diarrheal illness (gastroenteritis). Infants and young children are most likely to have diarrhea caused by astroviruses. However, since immunity acquired during childhood wanes over time, the elderly and those with compromised immune systems are also susceptible to infection. Like other viral infections, astroviruses tend to be more common at certain times of the year and spread quickly in areas with poor sanitation and where people are living in close quarters. While there is no specific treatment, vaccine, or cure, researchers are still learning about astroviruses and exploring potential ways to prevent and treat the illness they cause.