January 2025 Pathogen Roundup | Virus Update

Not one, not two but three viral surges are making the news as we roll into 2025: Norovirus, Avian Flu and HMPV. Each virus and situation is quite different. The latest facts on each are below.

Norovirus

What is Norovirus?

According to the Centers for Disease Control and Prevention (CDC), norovirus is a highly contagious group of viruses. Norovirus infection causes gastroenteritis (inflammation of the stomach and intestines). Norovirus illness can make you feel extremely sick with diarrhea and vomiting many times a day. Some people may get severely dehydrated, especially young children, the elderly, and people with other illnesses. Norovirus causes up to 71,000 hospitalizations and 570 to 800 deaths annually, mostly in young children and the elderly. Healthcare facilities and other institutional settings (e.g., daycare centers, schools, etc.) are particularly at-risk for outbreaks because of increased person-to-person contact.

How does it spread?

Noroviruses are found in the feces and vomit of infected people. This virus is very contagious and can spread rapidly throughout healthcare facilities. People can become infected with the virus in several ways:

• Having direct contact with another person who is infected (a healthcare worker, visitor, or another patient)

• Eating food or drinking liquids that are contaminated with norovirus

• Touching surfaces or objects contaminated with norovirus, and then touching your mouth or other food items

• Norovirus can stay on surfaces and still infect people for days or weeks. Norovirus can survive some disinfectants, making it hard to eliminate.

What is the latest information?

Norovirus cases are on the rise in the United States, with the Centers for Disease Control and Prevention (CDC) reporting nearly 500 cases from August to December 2024. There were 91 suspected or confirmed norovirus outbreaks in the first week of December, the most recent data available. This is a higher number than the C.D.C. has recorded during the same week in recent years. It also exceeds the number of outbreaks recorded in early December in the years leading up to the Covid-19 pandemic.

One strain, known as GII.17, accounts for nearly 70 percent of the outbreaks in the United States, C.D.C. data show. The strain also drove a surge of cases in Britain this season.

Avian Flu

What is it?

Avian influenza, or bird flu, is a broad term that refers to several types of influenza that normally infect birds. The bird flu that’s been making news in the United States is a virus called H5N1.

Some flu viruses carried by birds cause only mild infections and are classified as low-pathogenic viruses. In contrast, H5N1 often kills birds that catch it, so it is classified as a highly pathogenic avian influenza.

How does it spread?

H5N1, also known as avian influenza or bird flu, primarily spreads through contact with infected birds. Here are the main ways it can spread:

1. Direct Contact: The virus can be transmitted through direct contact with infected birds, including their saliva, nasal secretions, and feces.

2. Contaminated Environments: Surfaces contaminated with the virus, such as bird cages, water, and feed, can also be sources of infection.

3. Intermediate Hosts: In some cases, the virus can spread through an intermediate host, such as another animal that has been in contact with infected birds.

4. Human Infection: While rare, humans can become infected through close or prolonged unprotected contact with infected birds or contaminated environments. This can happen when the virus gets into a person's eyes, nose, or mouth, or is inhaled.

5. It's important to note that human-to-human transmission of H5N1 is extremely rare, but it remains a concern for public health officials due to the potential for the virus to mutate and spread more easily among people.

What is the latest information?

Avian flu, specifically the H5N1 strain, continues to affect poultry and wild birds in the United States. The CDC has reported several outbreaks in commercial poultry flocks across multiple states, including Delaware, Ohio, Indiana, North Carolina, Michigan, and California. The virus has also been detected in dairy cattle and wild birds.

There have been 66 confirmed human cases of H5N1 in the United States since the start of 2024 and one severe case resulting in the first human death reported, in early January 2025. While the risk of human-to-human transmission remains low, CDC is closely monitoring the situation.

HMPV

What is HMPV?

Human metapneumovirus (HMPV) is a respiratory virus that can cause both upper and lower respiratory infections. It was first identified in 2001 and belongs to the Pneumoviridae family, along with respiratory syncytial virus (RSV)2.

Symptoms: Common symptoms of HMPV include:

• Cough

• Fever

• Nasal congestion

• Shortness of breath

• Wheezing

• Difficulty breathing

• Chest pain

• Severe fatigue

• Dehydration

In severe cases, HMPV can lead to bronchitis or pneumonia.

How does it spread?

HMPV spreads through respiratory secretions from coughing and sneezing, close personal contact, and touching contaminated surfaces. The virus can be transmitted by touching the mouth, nose, or eyes after contact with contaminated surfaces. The estimated incubation period for HMPV is 3 to 6 days.

Prevention: To prevent the spread of HMPV, follow these steps:

• Wash hands frequently with soap and water for at least 20 seconds.

• Avoid touching your eyes, nose, or mouth with unwashed hands.

• Avoid close contact with sick individuals.

• Clean and disinfect frequently touched surfaces.

• Cover your mouth and nose when coughing or sneezing.

• Stay home when you are sick.

What is the current situation?

HMPV cases have been on the rise in several regions, including India and China. In India, there have been reports of HMPV infections in multiple states, with Gujarat confirming three cases, including an eight-year-old boy. The virus has also been detected in other states like Karnataka, Tamil Nadu, and Maharashtra.

Sources:

www.nytimes.com/2024/12/30/well/norovirus-symptoms-outbreak.html

www.cdc.gov/norovirus/index.html

www.cnn.com/2025/01/08/health/bird-flu-h5n1-pandemic-risk-explained/index.html

www.cdc.gov/media/releases/2024/m1218-h5n1-flu.html

www.cdc.gov/bird-flu/situation-summary/index.html

www.nytimes.com/2025/01/07/health/hmpv-virus-china.html

indianexpress.com/article/india/govt-lab-confirms-hmpv-infection-in-8-yr-old-cases-rise-to-three-in-gujarat-9772423/