Virus B from monkeys, the appeal of virologists: “Avoid direct contact”

“It is essential to try to avoid direct contact with monkeys as much as possible. If you are bitten or scratched by an infected animal, contagion cannot be ruled out” from Herpesvirus simiae, the B virus which affected a 37-year-old in Hong Kong attacked while hiking in a park. This is the warning issued by Arnaldo Carusopresident of the Italian Society of Virology (Siv-Isv), to those who are planning, perhaps for the summer holidays, trips to more or less exotic destinations.

“Even in the United States, for example in Florida – recalls the expert, full professor of microbiology and clinical microbiology at the University of Brescia and director of the Microbiology Laboratory of the Asst Spedali Civili – the existence of colonies of carrier monkeys has been documented of this pathogen, which appears to be spreading among animals.”

What is the B virus

“High risk of mortality” in human cases of virus B transmitted by monkeys, a Herpesvirus that “infects some primates” and which “can infect humans through bites or scratches by a monkey carrying the pathogen”. If the virus initially causes “local, flu-like symptoms” that can be treated with antiviral drugs, “in at least half of the cases the infection reaches the brain and when this happens death is highly probable”, continues Caruso. “Certainly – the expert stated – we are not talking about an epidemic danger, much less a pandemic”. However, it is “important to control the spread of the infection among monkeys” and “to know – he warns – that humans can also get sick if accidentally injured by an infected monkey”.

The case of the infected man in Hong Kong. Symptoms and treatments

The young man infected in Hong Kong arrived in hospital on March 21 with fever and loss of consciousness, and when the news spread at the beginning of April his condition was described as “critical”. According to family members, at the end of February the man was injured during a visit to Kam Shan Country Park, a hiking destination known for its troop of wild monkeys.

Infected people may initially present with local, flu-like symptoms, but they risk progressing to a central nervous system infection. “Frequent complications”, describes the president of the Italian virologists: they arise “at least in half of the cases” and that these patients can die “unfortunately it is very easy. As with all herpes viruses, also to treat Herpesvirus simiae in humans There are antiviral drugs (aciclovir, ganciclovir). Medicines that “must be given immediately as soon as the infection is suspected. Because if it reaches the brain the drugs can no longer act.” In these cases, there is little or nothing left to do.

Very rare human cases

Simian virus B “is a herpes virus,” Caruso explains. “Herpes viruses are very widespread – he recalls – while this virus in particular is limited to some monkeys, highlighted for the first time in the first decades of the last century in vervet monkeys and therefore also called ‘vervet monkey’ virus. For a long time it was more what more than a scientific curiosity. In the past, in fact – says the specialist – some laboratory workers who had to deal with monkeys for their experiments, working directly with these animals or handling their tissues or biological materials, happened to become infected. It was then understood that a scratch or bite from a monkey carrying this virus, or contact with its infected fluid, perhaps through an accidental cut, could make humans ill. And the infection could be serious, quickly fatal if it involved the central nervous system”.

“We therefore began to carry out analyzes on the monkeys that were imported for research and this danger, at the laboratory level or in any case of animals in captivity – underlines Caruso – was completely averted. However, the problem of ‘wild’ monkeys remained , freely in nature”.

Avoid direct contact

In recent years something has changed. “It is known that in the USA, for example in Florida – Caruso points out – there are colonies of monkeys carrying this virus which seems to be spreading within the colonies themselves. Even the monkeys, in fact, biting each other or through mutual contact, can transmit the B virus to each other”. And then there is the human case in Hong Kong, the first recorded by the autonomous territory in Southeast China.

All warning signs, because if “from a practical point of view today it seems difficult for a monkey to be able to have such contact with humans as to infect him, certainly – warns the expert – if this virus continues to spread among animals, and these animals come into contact with humans, the risk of transmission to humans increases. It is therefore necessary to control the infection within monkey populations and evaluate the colonies.”