People more often are origin of infectious diseases in animals than vice versa, data suggest

News brief
Woman cuddling dog
Alex Beattie / Flickr cc

People pass twice as many viruses to domestic and wild animals than animals pass to people, concludes a study today in Nature Ecology & Evolution.

University College London (UCL) researchers analyzed genomic data on nearly 12 million viruses in 32 viral families using network and evolutional analyses to characterize the mutations behind recent vertebrate species jumps.

Most emerging and re-emerging infectious diseases are caused by viruses that circulate naturally in nonhuman vertebrates. "When these viruses cross over into humans, they can cause disease outbreaks, epidemics and pandemics," they authors wrote. "While zoonotic host jumps have been extensively studied from an ecological perspective, little attention has gone into characterizing the evolutionary drivers and correlates underlying these events."

Viral strains that jump species had to mutate more

About twice as many species jumps were inferred to be from people to animals rather than the other way round, a pattern consistent across most viral families. "We further observe that the extent of adaptation associated with a host jump is lower for viruses with broader host ranges," they wrote. "Finally, we show that the genomic targets of natural selection associated with host jumps vary across different viral families, with either structural or auxiliary genes being the prime targets of selection."

The genomic targets of natural selection associated with host jumps vary across different viral families, with either structural or auxiliary genes being the prime targets of selection.

In a UCL news release, lead author Cedric Tan, a PhD student at the UCL Genetics Institute, said, "When animals catch viruses from humans, this can not only harm the animal and potentially pose a conservation threat to the species, but it may also cause new problems for humans by impacting food security if large numbers of livestock need to be culled to prevent an epidemic, as has been happening over recent years with the H5N1 bird flu strain."

"Additionally, if a virus carried by humans infects a new animal species, the virus might continue to thrive even if eradicated among humans, or even evolve new adaptations before it winds up infecting humans again," he added.

Vietnam confirms H5N1 in man's avian flu death

News brief

Vietnam's health ministry today announced that a recently reported H5 avian flu infection in Khanh Hoa province was the H5N1 subtype, according to a statement translated and posted by Avian Flu Diary, an infectious disease news blog.

NIAID/Flickr cc

The infection involved a 21-year-old college student whose H5 infection was initially reported last week by the media and was confirmed by provincial health authorities.

Today's health ministry statement has new details about the case, including that the patient died from his infection on March 23. Officials also said that an epidemiologic investigation found that the man had trapped wild birds near his home before and after the Lunar New Year holiday. No sick or dead poultry, however, were reported near the family's home.

No other cases have been detected during monitoring of the patient's contacts.

Questions remain about H5N1 clade

So far, it's not clear which H5N1 clade is involved in the man's infection. The older clade (—still circulating in some parts of Asia—has recently been connected to a spate of illnesses in Cambodia, many of them fatal. The newer clade ( affecting poultry in multiple world regions has also infected people in rare instances, mainly those who had exposure to infected birds or mammals.

Vietnam's last H5N1 case, reported in October 2022 from Phu Tho province, was its first since 2014. The clade involved was not reported in that case, either.

The health ministry said the country continues to report sporadic H5N1 detections in poultry and that agriculture ministry data show that six avian flu outbreaks have been reported across six provinces, including Khanh Hoa, where the man lived.

FDA OKs Invivyd's COVID preventive Pemgarda for emergency use

News brief

The Food and Drug Administration (FDA) on March 22 granted emergency use authorization (EUA) for Invivyd's monoclonal antibody to prevent COVID-19 in immunocompromised patients, which fills a gap following the withdrawal of Evusheld in January 2023.

iv drip
Amornrat Phuchom / iStock

The monoclonal antibody, called pemivibart (Pemgarda), is authorized for pre-exposure prophylaxis in adolescents and adults with moderate-to-severe immunocompromise, such as solid-organ transplant recipients and those with blood cancers. The drug is given as a 4,500-milligram intravenous infusion. The company had submitted its EUA request in early January.

The FDA based its EUA on clinical trials that suggested pemivibart had neutralizing activity against SARS-CoV-2 variants, including JN.1, which is currently dominant in the United States and abroad.

In its announcement, the company, based in Massachusetts, also said pemivibart is its first pre-exposure monoclonal antibody to receive an EUA based on a novel, rapid, and repeatable immunobridging trial design, which it said will help address ongoing viral evolution.

Drug will be available for ordering soon

Dave Hering, Invivyd's chief executive officer, said in the statement that the company expects to have the product available for ordering "imminently" and that an initial supply has already been packaged and is awaiting release at a US-based third-party logistics provider.

He also added that the company has plans to explore pemivibart as a treatment for symptomatic COVID infection.

CDC releases ventilation guidance for curbing indoor respiratory virus spread

News brief

As part of its updates on strategies to battle respiratory viruses, the US Centers for Disease Control and Prevention (CDC) on March 22 detailed steps that people can take to reduce the number of respiratory particles that circulate in indoor air. The ventilation guidance update comes as respiratory disease levels such as flu and COVID are declining from a late December peak.

giant fan
Adam Winsor/Flickr cc

The CDC said ventilation, alongside vaccination and practicing good hand hygiene, is one of the core strategies for protecting people against respiratory illness. "People can still get sick after ventilating a space, so it is important to use ventilation as one part of a multi-layered approach to protect ourselves against getting sick from respiratory viruses," the CDC said.

Steps for improving ventilation are useful year-round, but are especially helpful when virus levels are high in the community, when people are exposed, sick, or recovering, or when people have risk factors for severe illness, the agency added.

Tips for optimizing HVAC systems, adding other steps

The guidance emphasizes the importance of bringing in fresh outdoor air and ensuring that air conditioning and heating systems are operating properly, preferably with filters rated MERV-13 or higher. It also describes other steps that can be added, including air circulation, proper exhaust venting, air cleaners, and ultraviolet air treatment.

The CDC also said portable carbon dioxide monitors can help determine the staleness or freshness of indoor air. "If possible, move activities outdoors to lower the risk of virus transmission," the CDC said.

Chick-Fil-A to modify its policy on antibiotic use

News brief
Althom / iStock

Fast-food chain Chick-Fil-A says a change is coming to its policy on antibiotic use in its chicken supply.

In a statement issued over the weekend, Chick-Fil-A says it will shift its policy this spring from No Antibiotics Ever to No Antibiotics Important to Human Medicine. That means the company will allow its chicken suppliers to use antibiotics intended for animals to treat sick birds and flocks but will not allow the use of antibiotics that are also used in human medicine.

A Chick-Fil-A official told the Associated Press that the decision reflects concerns about the company's ability to acquire a sufficient supply of antibiotic-free chickens.

A consumer-driven shift

Chick-Fil-A is one of several fast-food chains that, along with the country's biggest poultry producers, have made the move to antibiotic-free chicken in response to consumer pressure over the past decade. Use of medically important antibiotics in poultry production has significantly fallen during that period. According to the most recent report from the Food and Drug Administration's Center for Veterinary Medicine, poultry accounted for only 2% of medically important antibiotic sales in 2022.

Antibiotic stewardship advocates argue that widespread use of medically important antibiotics in food-producing animals is contributing to the emergence and spread of antimicrobial resistance.

In July 2023, Tyson Foods made a similar announcement, saying it was dropping its No Antibiotics Ever label from some of its chicken products and would use a new label clarifying that its chickens are not given medically important antibiotics. The company said it made that decision because it was reintroducing ionophores, which are not considered medically important antibiotics, into its chickens' diets.

Study: Long COVID affects 8% of those with COVID-19, is more common in women

News brief


tured woman
brizmaker / iStock

New national data in France reveals that, by the World Health Organization (WHO) definition, the prevalence of long COVID is 4.0% in the French population overall and 8.0% among people who had COVID-19.

Among the 8.0%, the prevalence varied from 5.3% in men who had COVID-19, to 14.9% among the unemployed, and 18.6% of those with a history of hospitalization for COVID-19. The study is published in Clinical Microbiology and Infection.

The study is based on a cross-sectional survey of 10,615 participants conducted in August through November 2022. The WHO defines long COVID as "continuation or development of new symptoms 3 months after the initial SARS-CoV-2 infection, with these symptoms lasting for at least 2 months with no other explanation."

A total of 5,781 (54.5%) of study participants reported ever having a SARS-CoV-2 infection. Among those with lasting symptoms, fatigue was the most common, followed by sleep disorders, anxiety, and joint pain. According to the WHO definition, long COVID prevalence was 4.0% (95% confidence interval [CI], 3.6% to 4.5%) in the overall population.

Prevalence twice as high in women

"Prevalence was more than twice as high in women than in men and 68% higher in unemployed people; it was two to three times lower among elderly participants and lower among participants living alone," the authors wrote.

Prevalence was more than twice as high in women than in men and 68% higher in unemployed people.

Prevalence dropped to 2.4% when the WHO definition was strengthened with requiring at least moderate impact on daily activities (95% CI, 2.1% to 2.8%), and dropped further to 1.2% when the definition included only participants reporting strong or very strong impact of symptoms on daily activities.

More than half of those with WHO-defined long COVID were infected during the Delta wave, but the authors said ongoing surveillance of long COVID should take place. "Long COVID and especially the forms with a strong impact on daily activities will continue to represent a significant burden for the societies and healthcare systems of most countries, thus warranting ongoing surveillance," they concluded.

This week's top reads